mapping_set_error: add unlikely()

This is called on a per-page basis and in the vast majority of cases
`error' is zero.

Cc: Guillaume Chazarain <guichaz@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 file changed