media: uvcvideo: queue: Simplify spin-lock usage

Both uvc_start_streaming(), and uvc_stop_streaming() are called from
userspace context, with interrupts enabled. As such, they do not need to
save the IRQ state, and can use spin_lock_irq() and spin_unlock_irq()
respectively.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>