fs/ramfs/file-nommu.c needs include/linux/sched.h

This file makes use of various macros defined in files like asm/current.h
or asm-generic/resource.h.  All these files can be included via sched.h.
The building of the !MMU ARM kernel (with additional patches) fails
without this change.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>