knfsd: clean up EX_RDONLY

Share a little common code, reverse the arguments for consistency, drop the
unnecessary "inline", and lowercase the name.

Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Acked-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>