usb: renesas_usbhs: fix spinlock suspected in a gadget complete function

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

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>