ASoC: wm5100: match wait_for_completion_timeout return type

return type of wait_for_completion_timeout is unsigned long not int. An
appropriately named unsigned long is added and the assignment fixed up.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>