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>

diff --git a/drivers/usb/otg/Kconfig b/drivers/usb/otg/Kconfig
index fc1ca03..aa884d0 100644
--- a/drivers/usb/otg/Kconfig
+++ b/drivers/usb/otg/Kconfig
@@ -43,7 +43,7 @@
 
 config TWL4030_USB
 	tristate "TWL4030 USB Transceiver Driver"
-	depends on TWL4030_CORE
+	depends on TWL4030_CORE && REGULATOR_TWL4030
 	select USB_OTG_UTILS
 	help
 	  Enable this to support the USB OTG transceiver on TWL4030