usb: gadget: udc: renesas_usb3: Fix usb_gadget_giveback_request() calling

According to the gadget.h, a "complete" function will always be called
with interrupts disabled. However, sometimes usb3_request_done() function
is called with interrupts enabled. So, this function should be held
by spin_lock_irqsave() to disable interruption. Also, this driver has
to call spin_unlock() to avoid spinlock recursion by this driver before
calling usb_gadget_giveback_request().

Reported-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
Tested-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
Fixes: 746bfe63

 ("usb: gadget: renesas_usb3: add support for Renesas USB3.0 peripheral controller")
Cc: <stable@vger.kernel.org> # v4.5+
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>