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.

This patch also fixes a bug where the driver didn't release the
IRQ.

v2:
	* automatically release IRQ via devm_request_irq() (Paul)
	* mention the bugfix (Sam)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210715100258.6638-1-tzimmermann@suse.de