twl4030 usb regulator support tweaks

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

 (a) always overwrite the old list of consumers ... else
     the regulators all share 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: Tony Lindgren <tony@atomide.com>