[PATCH] fix warning in arch/ppc/boot/simple/misc.c

From: Christoph Hellwig <hch@lst.de>

asm-ppc/elf.h uses a pointer to struct task_struct without any
forward-declaration.

In file included from include/linux/elf.h:5,
                 from arch/ppc/boot/simple/misc.c:20:
include/asm/elf.h:102: warning: `struct task_struct' declared inside parameter list
include/asm/elf.h:102: warning: its scope is only this definition or declaration, which is probably not what you want

include/asm-ppc/elf.h

@@ -74,6 +74,8 @@ typedef elf_vrreg_t elf_vrregset_t[ELF_NVRREG];
 
 #ifdef __KERNEL__
 
+struct task_struct;
+
 /*
  * This is used to ensure we don't load something for the wrong architecture.
  */