usb: musb: mpfs: add missing clk_disable_unprepare() in mpfs_remove()

usb: musb: mpfs: add missing clk_disable_unprepare() in mpfs_remove()

clock source is prepared and enabled by clk_prepare_enable()
in probe function, but no disable or unprepare in remove.

Fixes: 7a96b6ea90a4 ("usb: musb: Add support for PolarFire SoC's musb controller")
Reported-by: Hulk Robot <hulkci@huawei.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220628140527.1404439-1-yangyingliang@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>