twl4030-regulator: list more VAUX4 voltages

The VAUX4 voltage table scrolls onto a second page in many versions
of the TWL4030 family manuals.  This doesn't mean we should ignore
those values!  Some boards use the (fully supported) 2.8V setting.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>