vga: merge conditionals on shift control register

There are two sets of conditionals using the shift control bits: one to
verify the palette and adjust disp_width, one to compute the "v" and
"bits" variables.  Merge them into one, with the extra benefit that
we now have the "bits" value available early and can use it to
compute region_end.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/hw/display/vga.c b/hw/display/vga.c
index bc5b834..4795a00 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1546,12 +1546,54 @@
     }
 
     if (shift_control == 0) {
+        full_update |= update_palette16(s);
         if (sr(s, VGA_SEQ_CLOCK_MODE) & 8) {
             disp_width <<= 1;
+            v = VGA_DRAW_LINE4D2;
+        } else {
+            v = VGA_DRAW_LINE4;
         }
+        bits = 4;
+
     } else if (shift_control == 1) {
+        full_update |= update_palette16(s);
         if (sr(s, VGA_SEQ_CLOCK_MODE) & 8) {
             disp_width <<= 1;
+            v = VGA_DRAW_LINE2D2;
+        } else {
+            v = VGA_DRAW_LINE2;
+        }
+        bits = 4;
+
+    } else {
+        switch (depth) {
+        default:
+        case 0:
+            full_update |= update_palette256(s);
+            v = VGA_DRAW_LINE8D2;
+            bits = 4;
+            break;
+        case 8:
+            full_update |= update_palette256(s);
+            v = VGA_DRAW_LINE8;
+            bits = 8;
+            break;
+        case 15:
+            v = s->big_endian_fb ? VGA_DRAW_LINE15_BE : VGA_DRAW_LINE15_LE;
+            bits = 16;
+            break;
+        case 16:
+            v = s->big_endian_fb ? VGA_DRAW_LINE16_BE : VGA_DRAW_LINE16_LE;
+            bits = 16;
+            break;
+        case 24:
+            v = s->big_endian_fb ? VGA_DRAW_LINE24_BE : VGA_DRAW_LINE24_LE;
+            bits = 24;
+            break;
+        case 32:
+            v = s->big_endian_fb ? VGA_DRAW_LINE32_BE : VGA_DRAW_LINE32_LE;
+            bits = 32;
+            break;
         }
     }
 
@@ -1607,53 +1649,6 @@
         }
     }
 
-    if (shift_control == 0) {
-        full_update |= update_palette16(s);
-        if (sr(s, VGA_SEQ_CLOCK_MODE) & 8) {
-            v = VGA_DRAW_LINE4D2;
-        } else {
-            v = VGA_DRAW_LINE4;
-        }
-        bits = 4;
-    } else if (shift_control == 1) {
-        full_update |= update_palette16(s);
-        if (sr(s, VGA_SEQ_CLOCK_MODE) & 8) {
-            v = VGA_DRAW_LINE2D2;
-        } else {
-            v = VGA_DRAW_LINE2;
-        }
-        bits = 4;
-    } else {
-        switch(s->get_bpp(s)) {
-        default:
-        case 0:
-            full_update |= update_palette256(s);
-            v = VGA_DRAW_LINE8D2;
-            bits = 4;
-            break;
-        case 8:
-            full_update |= update_palette256(s);
-            v = VGA_DRAW_LINE8;
-            bits = 8;
-            break;
-        case 15:
-            v = s->big_endian_fb ? VGA_DRAW_LINE15_BE : VGA_DRAW_LINE15_LE;
-            bits = 16;
-            break;
-        case 16:
-            v = s->big_endian_fb ? VGA_DRAW_LINE16_BE : VGA_DRAW_LINE16_LE;
-            bits = 16;
-            break;
-        case 24:
-            v = s->big_endian_fb ? VGA_DRAW_LINE24_BE : VGA_DRAW_LINE24_LE;
-            bits = 24;
-            break;
-        case 32:
-            v = s->big_endian_fb ? VGA_DRAW_LINE32_BE : VGA_DRAW_LINE32_LE;
-            bits = 32;
-            break;
-        }
-    }
     vga_draw_line = vga_draw_line_table[v];
 
     if (!is_buffer_shared(surface) && s->cursor_invalidate) {