usb: chipidea: msm: add remove method

allow this driver to be removed too.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Richard Zhao <richard.zhao@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>