drm/atmel-hlcdc: Convert to Linux IRQ interfaces

Drop the DRM IRQ midlayer in favor of Linux IRQ interfaces. DRM's
IRQ helpers are mostly useful for UMS drivers. Modern KMS drivers
don't benefit from using it. DRM IRQ callbacks are now being called
directly or inlined.

v2:
	* use managed release via devm_request_irq() (Sam)
	* drop extra test for irq != IRQ_NOTCONNECTED (Sam)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Dan Sneddon <Dan.Sneddon@microchip.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210803090704.32152-4-tzimmermann@suse.de