mfd: twl4030 regulator bug fixes

This contains two bugfixes to the initial twl4030 regulator
support patch related to USB:

 (a) always overwrite the old list of consumers ... else
     the regulator handles all use the same "usb1v5" name;
 (b) don't set up the "usbcp" regulator, which turns out
     to be managed through separate controls, usually ULPI
     directly from the OTG controller.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Samuel Ortiz <sameo@openedhand.com>