target-xtensa: add FP registers

There are 16 32-bit FP registers (f0 - f15), control and status user
registers (fcr, fsr).

See ISA, 4.3.10 for more details.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/gdbstub.c b/gdbstub.c
index a91709f..d02ec75 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1696,6 +1696,10 @@
         GET_REG32(env->uregs[reg->targno & 0xff]);
         break;
 
+    case 4: /*f*/
+        GET_REG32(float32_val(env->fregs[reg->targno & 0x0f]));
+        break;
+
     case 8: /*a*/
         GET_REG32(env->regs[reg->targno & 0x0f]);
         break;
@@ -1736,6 +1740,10 @@
         env->uregs[reg->targno & 0xff] = tmp;
         break;
 
+    case 4: /*f*/
+        env->fregs[reg->targno & 0x0f] = make_float32(tmp);
+        break;
+
     case 8: /*a*/
         env->regs[reg->targno & 0x0f] = tmp;
         break;