regulator: rc5t583: Correct MODULE LICENSE to GPL v2

Fixing build issue reported by Paul Gortmaker:

It appears this breaks linux-next allmodconfig build, because it
uses an uppercase V in the v2 of its MODULE_LICENSE.

FATAL: modpost: GPL-incompatible module rc5t583-regulator.ko uses
GPL-only symbol 'platform_driver_unregister'
make[2]: *** [__modpost] Error 1

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>