ARM: sun6i: Add support for the power reset control module found on the A31

ARM: sun6i: Add support for the power reset control module found on the A31

The A31 has a new module called PRCM, or Power, Reset Control Module.
This module controls clocks and resets for RTC block modules, and also
PLL biasing in the main clock module.

This patch adds the register definitions, and also enables the clocks
and resets for the RTC block PIO (pin controller) and P2WI (push-pull
2 wire interface) which is used to talk to the PMIC.

Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
[wens@csie.org: spacing fixes reported by checkpatch.pl]
[wens@csie.org: Use setbits helper in PRCM init function]
[wens@csie.org: rephrase commit message to explain what the hardware
		supports and what we actually enable]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Ian Campbell <ijc@hellion.org.uk>