target-ppc: Fix SRR0 when taking unaligned exceptions

We are setting SRR0 to the instruction before the one causing the
unaligned exception. A quick testcase:

. = 0x100
.globl _start
_start:
	/* Cause a 0x600 */
	li	3,0x1
	stwcx.	3,0,3
1:	b	1b

. = 0x600
1:	b	1b

Built into something we can load as a BIOS image:

gcc -mbig -c test.S
ld -EB -Ttext 0x0 -o test test.o
objcopy -O binary test test.bin

Run with:

qemu-system-ppc64 -nographic -bios test.bin

Shows an incorrect SRR0 (points at the li):

SRR0 0000000000000100

With the patch we get the correct SRR0:

SRR0 0000000000000104
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NAlexander Graf <agraf@suse.de>

linux-user/main.c

@@ -1650,7 +1650,7 @@ void cpu_loop(CPUPPCState *env)
             info.si_signo = TARGET_SIGBUS;
             info.si_errno = 0;
             info.si_code = TARGET_BUS_ADRALN;
-            info._sifields._sigfault._addr = env->nip - 4;
+            info._sifields._sigfault._addr = env->nip;
             queue_signal(env, info.si_signo, &info);
             break;
         case POWERPC_EXCP_PROGRAM:  /* Program exception                     */

target-ppc/excp_helper.c

@@ -200,7 +200,7 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int excp_model, int excp)
         /* Get rS/rD and rA from faulting opcode */
         env->spr[SPR_DSISR] |= (cpu_ldl_code(env, (env->nip - 4))
                                 & 0x03FF0000) >> 16;
-        goto store_current;
+        goto store_next;
     case POWERPC_EXCP_PROGRAM:   /* Program exception                        */
         switch (env->error_code & ~0xF) {
         case POWERPC_EXCP_FP: