powerpc: Fixes to get the merged kernel to boot on powermac.

This merges ppc_ksyms.c, puts back the actual do_execve call in
sys_execve, makes init_MMU call find_end_of_memory rather than
ppc_md.find_end_of_memory (every platform has a device tree
with a /memory node now, right?) and fixes some problems with the
mpic initialization on newworld powermacs.

Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/mm/init.c

@@ -239,7 +239,7 @@ void __init MMU_init(void)
 	if (boot_mem_size)
 		total_memory = boot_mem_size;
 	else
-		total_memory = ppc_md.find_end_of_memory();
+		total_memory = find_end_of_memory();
 
 	if (__max_memory && total_memory > __max_memory)
 		total_memory = __max_memory;