usb: gadget: udc: remove comparison to bool in mv_u3d_core.c

Fix the following coccicheck warning:

drivers/usb/gadget/udc/mv_u3d_core.c:1551:5-13: WARNING: Comparison to
bool

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>