Fix powerpc 604 reset vector

According to 604eUM_book (see 8.3.3 Reset inputs p8-54), the IP bit is set
for hreset and the vector is at offset 0x100 from the exception prefix.

No difference in this area between 604 and 604e.

Signed-off-by: Tristan Gingold <gingold@adacore.com>
diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index 1c2aca8..f5e3b28 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -2875,9 +2875,9 @@
     env->excp_vectors[POWERPC_EXCP_PERFM]    = 0x00000F00;
     env->excp_vectors[POWERPC_EXCP_IABR]     = 0x00001300;
     env->excp_vectors[POWERPC_EXCP_SMI]      = 0x00001400;
-    env->hreset_excp_prefix = 0x00000000UL;
+    env->hreset_excp_prefix = 0xFFF00000UL;
     /* Hardware reset vector */
-    env->hreset_vector = 0xFFFFFFFCUL;
+    env->hreset_vector = 0x00000100UL;
 #endif
 }