media: imx-pxp: Use non-threaded IRQ

There's no need to use threaded IRQs with the PXP, as the interrupt
handler doesn't need to sleep and doesn't perform any time-consuming
operation. Switch to regular IRQ handler.

This fixes lockups of the PXP noticed on i.MX7, where the PXP would stop
generating interrupts after a variable number of frames (from a few
dozens to a few hundreds). The root cause is however unknown.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>