regulator: Fix the argument of calling regulator_mode_constrain

The second parameter of regulator_mode_constrain takes a pointer.

This patch fixes below warning:
drivers/regulator/core.c: In function 'regulator_set_mode':
drivers/regulator/core.c:2014: warning: passing argument 2 of 'regulator_mode_constrain' makes pointer from integer without a cast
drivers/regulator/core.c:200: note: expected 'int *' but argument is of type 'unsigned int'

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@vega.(none)>