ARM: sunxi: dt: add PRCM clk and reset controller subdevices

Add DT definitions for PRCM (Power/Reset/Clock Management) clock and reset
controller subdevices.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>