usb: Add Intel Langwell USB OTG Transceiver Driver

usb: Add Intel Langwell USB OTG Transceiver Driver

This adds support for the USB transceiver driver in the Langwell chipset used
on the Intel MID platforms. It folds up the original patch set which includes
basic support for the device, PHY low power mode (Please notice that there is
a limitation, after we drive VBus down, 2ms delay is required from SCU FW to
sync up OTGSC register with USBCFG register), software timers (the hardware
timers do not work in low power mode), HNP, SRP.

Signed-off-by: Hao Wu <hao.wu@intel.com>
Signed-off-by: Alek Du <alek.du@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>