Fix compile warnings from w100fb.c.  Attribute registration failure doesn't
stop the driver working so just warn about it.
Signed-off-by: NRichard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAntonino Daplas <adaplas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>