[media] adv7604: Add support for hardware reset

The part can be reset by a low pulse on the RESET pin (i.e. a hardware
reset) with a minimum width of 5 ms. It is recommended to wait 5 ms
after the low pulse before an I2C write is performed to the part.
For safety reasons, the delays will be between 5 and 10 ms.

The RESET pin can be tied high, so the GPIO is optional.

Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>