ARM: sun8i: Add PRCM clock and reset controller nodes to the DTSI

With sun8i PRCM support available, we can add the PRCM clock and
reset controller nodes to the DTSI. Also update R_UART's clock
phandle and add it's reset control phandle.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>