power: reset: at91-reset: add reset_controller_dev support

SAMA7G5 reset controller has 5 extra lines that goes to different devices
(3 lines to USB PHYs, 1 line to DDR controller, 1 line to DDR PHY
controller). These reset lines could be requested by different controller
drivers (e.g. USB PHY driver) and these controllers' drivers could
assert/deassert these lines when necessary. Thus add support for
reset_controller_dev which brings this functionality.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>