i2c: sun8i_rsb: Add support for DM clocks and resets

Currently, clock/reset setup for this device is handled by a
platform-specific function and is intermixed with non-DM pinctrl
setup. Use the devicetree to get clocks/resets, which disentagles
it from the pinctrl setup in preparation for moving to DM_PINCTRL.

This also has the added benefit of picking the right clock/reset
bits for H6 and new SoCs that have a rearranged PRCM MMIO space.

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