USB: TWL: disable VUSB regulators when cable unplugged

This patch disables USB regulators VUSB1V5, VUSB1V8, and VUSB3V1
when the USB cable is unplugged to reduce power consumption.
Added a depencency from twl4030 usb driver to TWL_REGULATOR.

Signed-off-by: Jouni Hogander <jouni.hogander@nokia.com>
Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@digia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>