clk: sunxi: Add sun9i A80 apbs gates support

This patch adds support for the PRCM apbs clock gates found on the
Allwinner A80 SoC.

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