serial: Add MemoryRegion parameter to serial_mm_init

Remove the get_system_memory() call from serial_mm_init, pushing
it back into the callers.  In many cases we already have the
system memory region available.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/hw/musicpal.c b/hw/musicpal.c
index 2131db1..20553b5 100644
--- a/hw/musicpal.c
+++ b/hw/musicpal.c
@@ -1486,12 +1486,12 @@
                           pic[MP_TIMER4_IRQ], NULL);
 
     if (serial_hds[0]) {
-        serial_mm_init(MP_UART1_BASE, 2, pic[MP_UART1_IRQ], 1825000,
-                       serial_hds[0], DEVICE_NATIVE_ENDIAN);
+        serial_mm_init(address_space_mem, MP_UART1_BASE, 2, pic[MP_UART1_IRQ],
+                       1825000, serial_hds[0], DEVICE_NATIVE_ENDIAN);
     }
     if (serial_hds[1]) {
-        serial_mm_init(MP_UART2_BASE, 2, pic[MP_UART2_IRQ], 1825000,
-                       serial_hds[1], DEVICE_NATIVE_ENDIAN);
+        serial_mm_init(address_space_mem, MP_UART2_BASE, 2, pic[MP_UART2_IRQ],
+                       1825000, serial_hds[1], DEVICE_NATIVE_ENDIAN);
     }
 
     /* Register flash */