drm/i2c: tda998x: use irq for connection status and EDID read

This patch adds the optional treatment of the tda998x IRQ.

The interrupt function is used to know the display connection status
without polling and to speedup reading the EDID.

The IRQ number and trigger type are defined in the i2c client either
by platform data or in the DT.

Tested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>