Amend the ab8500-usb driver to optionally take a pin control handle and
set the state of the pins to "default" on ab8500_usb_phy_enable and to
"sleep" on ab8500_usb_phy_disable.
The pinctrl handle is released on ab8500_usb_phy_disable because USB
pins are shared with ab8505_micro_usb_iddet driver.