i.MX usb controllers share non-core registers, which may include
SoC specific controls. We turn it into a usbmisc device and usbmisc
driver set operations needed by ci13xxx_imx driver.

For example, Sabrelite board has bad over-current design, we can
usbmisc to disable over-current detection.
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Richard Zhao <richard.zhao@freescale.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>