usb: add ab8500 usb transceiver driver

Basic driver for ab8500 usb otg transceiver

TODO:
-Regulators support
-Host and OTG testing
-Interface with PRCMU
-Charging support

Signed-off-by: Mian Yousaf Kaukab <mian.yousaf.kaukab@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>