ppc: Move load and store helpers, switch to AREG0 free mode

Add an explicit CPUPPCState parameter instead of relying on AREG0
and rename op_helper.c (which only contains load and store helpers)
to mem_helper.c. Remove AREG0 swapping in
tlb_fill().

Switch to AREG0 free mode. Use cpu_ld{l,uw}_code in translation
and interrupt handling, cpu_{ld,st}{l,uw}_data in loads and stores.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/target-ppc/excp_helper.c b/target-ppc/excp_helper.c
index 7fa7a59..c7762b9 100644
--- a/target-ppc/excp_helper.c
+++ b/target-ppc/excp_helper.c
@@ -179,7 +179,8 @@
         }
         /* XXX: this is false */
         /* Get rS/rD and rA from faulting opcode */
-        env->spr[SPR_DSISR] |= (ldl_code((env->nip - 4)) & 0x03FF0000) >> 16;
+        env->spr[SPR_DSISR] |= (cpu_ldl_code(env, (env->nip - 4))
+                                & 0x03FF0000) >> 16;
         goto store_current;
     case POWERPC_EXCP_PROGRAM:   /* Program exception                        */
         switch (env->error_code & ~0xF) {