mmc-twl4030 uses regulator framework

Finish decoupling the HSMMC glue from the twl4030 as the only
regulator provider, using the regulator framework instead.
This makes the glue's "mmc-twl4030" name become a complete
misnomer ... this code could probably all migrate into the
HSMMC driver now.

Tested on 3430SDP (SD and low-voltage MMC) and Beagle (SD),
plus some other boards (including Overo) after they were
converted to set up MMC regulators properly.

Eventually all boards should just associate a regulator with
each MMC controller they use.  In some cases (Overo MMC2 and
Pandora MMC3, at least) that would be a fixed-voltage regulator
with no real software control.  As a temporary hack (pending
regulator-next updates to make the "fixed.c" regulator become
usable) there's a new ocr_mask field for those boards.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>