PPC/GDB: handle read and write of fpscr

Although the support of this register may be uncomplete, there are no
reason to prevent the debugger from reading or writing it.

Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

gdbstub.c

@@ -781,7 +781,8 @@ static int cpu_gdb_write_register(CPUPPCState *env, uint8_t *mem_buf, int n)
             /* fpscr */
             if (gdb_has_xml)
                 return 0;
-            return 4;
+            store_fpscr(env, ldtul_p(mem_buf), 0xffffffff);
+            return sizeof(target_ulong);
         }
     }
     return 0;