[PATCH] sync_file_range(): use unsigned for flags

Ulrich suggested that the `flags' arg to sync_file_range() become unsigned.

Cc: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>