gpio: viperboard: Replace 'unsigned' with 'unsigned int'

Fixes a couple of warnings by checkpatch and sparse.

Signed-off-by: Hennie Muller <hm@bitlabs.co.za>
Link: https://lore.kernel.org/r/20190721125259.13990-1-hm@bitlabs.co.za


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>