reset: sunxi: Convert driver private data to platform data

The reason here is the same as the reason for changing the clock driver:
platform data can be provided when binding the driver.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>