usb: gadget: r8a66597: Fix a possible sleep-in-atomic-context bugs in r8a66597_queue()

The driver may sleep in an interrupt handler.
The function call path (from bottom to top) in Linux-4.16.7 is:

[FUNC] r8a66597_queue(GFP_KERNEL)
drivers/usb/gadget/udc/r8a66597-udc.c, 1193:
		r8a66597_queue in get_status
drivers/usb/gadget/udc/r8a66597-udc.c, 1301:
		get_status in setup_packet
drivers/usb/gadget/udc/r8a66597-udc.c, 1381:
		setup_packet in irq_control_stage
drivers/usb/gadget/udc/r8a66597-udc.c, 1508:
		irq_control_stage in r8a66597_irq (interrupt handler)

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.

This bug is found by my static analysis tool (DSAC-2) and checked by
my code review.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>