twl4030-regulator: expose VPLL2

Add VPLL2 to the set of twl4030-family regulators exposed for
use by various drivers.  It's commonly used to power the digital
video outputs (e.g. LCD or DVI displays) on OMAP3 systems.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>