clk: sunxi: Add muxable ahb factors clock for sun5i and sun7i

The AHB clock on sun5i and sun7i are muxable divider clocks.
Use a factors clock to support them.

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