regulator: core: Correct type of mode in regulator_mode_constrain

Every function handling the mode within the regulator core uses an unsigned
int for mode, except for regulator_mode_constrain. This patch changes the
type of mode within regulator_mode_constrain which fixes several instances
where we are passing pointers to unsigned ints then treating them as an int
within this function.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>