usb: otg: make twl6030_usb as a comparator driver to omap_usb2

All the PHY configuration other than VBUS, ID GND and OTG SRP are removed
from twl6030. The phy configurations are taken care by the dedicated
usb2 phy driver. So twl6030 is made as comparator driver for VBUS and
ID detection.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>