powerpc: provide ppc_md.panic() for both ppc32 & ppc64

Allow boards to provide a panic callback on ppc32.  Moved the code to sets
this up into setup-common.c so its shared between ppc32 & ppc64.  Also moved
do_init_bootmem prototype into setup.h.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/setup.h b/arch/powerpc/kernel/setup.h
index 2ebba75..e67066c 100644
--- a/arch/powerpc/kernel/setup.h
+++ b/arch/powerpc/kernel/setup.h
@@ -2,5 +2,7 @@
 #define _POWERPC_KERNEL_SETUP_H
 
 void check_for_initrd(void);
+void do_init_bootmem(void);
+void setup_panic(void);
 
 #endif /* _POWERPC_KERNEL_SETUP_H */