regulator: Convert virtual and userspace regulator consumer drivers to use module_pla...

This patch converts virtual and userspace regulator consumer drivers to use the
module_platform_driver() macro which makes the code smaller and a bit simpler.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>