clk: sunxi: make factors_clk_setup return the clock it registers

We will be needing this to register a factor clock as parent with leaf
divisors on a single call.

Signed-off-by: Emilio López <emilio@elopez.com.ar>
Acked-by: Mike Turquette <mturquette@linaro.org>

diff --cc drivers/clk/sunxi/clk-sunxi.c
Simple merge