USB: add Freescale USB OTG Transceiver driver

Slightly reworked and cleaned up driver from Freescale LTIB
for MPC5121E. The driver has been ported to the current kernel,
proc interface "/proc/driver/fsl_usb2_otg" has been replaced by
sysfs interface.

Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>