usb: gadget: udc: renesas_usb3: fix deadlock by spinlock

This patch fixes an issue that this driver is possible to cause
deadlock by double-spinclocked in renesas_usb3_stop_controller().
So, this patch removes spinlock API calling in renesas_usb3_stop().
(In other words, the previous code had a redundant lock.)

Fixes: 746bfe63

 ("usb: gadget: renesas_usb3: add support for Renesas USB3.0 peripheral controller")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>