ARM: sunxi: select MFD_SUN6I_PRCM when sun8i arch support is enabled

Select the MFD_SUN6I_PRCM option when sun8i arch is enabled in order to
get the PRCM (Power/Reset/Clock Management) related drivers compiled.

Also select ARCH_HAS_RESET_CONTROLLER and RESET_CONTROLLER to make sure
the reset controller drivers are compiled.

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