[PATCH] Fix linux/nfsd/const.h for make headers_check

make headers_check fails on linux/nfsd/const.h.

Since linux/sunrpc/msg_prot.h does not seem to export anything interesting
for userspace, this patch moves it in the __KERNEL__ protected section.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>