The codec reset pin is connected to several peripherals.  When the
reset is released, unfortunately the ADV7171 powers itself up rather
than remaining in power-down mode.  As we don't have a driver for
this device, we end up needlessly consuming an additional 330mW.

Not only that but we should have a way to arbitrate the reset signal.

This patch provides that facility: we program the ADV7171 to sleep
mode whenever the reset is released, and we release the reset when
any one of the three peripherals requests the reset to be released.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>