PPC: Provide zero SVR for -cpu e500mc and e5500

Even though our -cpu types for e500mc and e5500 are no real CPUs that
actually have version registers, a guest might still want to access
said version register and that has to succeed for a guest to be happy.

So let's expose a zero SVR value on E500_SVR SPR reads.
Signed-off-by: NAlexander Graf <agraf@suse.de>

target-ppc/translate_init.c

@@ -8633,9 +8633,9 @@ static const ppc_def_t ppc_defs[] = {
     POWERPC_DEF("e500v2_v22",    CPU_POWERPC_e500v2_v22,             e500v2),
     /* PowerPC e500v2 v3.0 core                                              */
     POWERPC_DEF("e500v2_v30",    CPU_POWERPC_e500v2_v30,             e500v2),
-    POWERPC_DEF("e500mc",        CPU_POWERPC_e500mc,                 e500mc),
+    POWERPC_DEF_SVR("e500mc", CPU_POWERPC_e500mc, POWERPC_SVR_E500,  e500mc),
 #ifdef TARGET_PPC64
-    POWERPC_DEF("e5500",         CPU_POWERPC_e5500,                  e5500),
+    POWERPC_DEF_SVR("e5500",    CPU_POWERPC_e5500, POWERPC_SVR_E500, e5500),
 #endif
     /* PowerPC e500 microcontrollers                                         */
     /* MPC8533                                                               */