clk: sunxi: register clock gates with clkdev

The new important clock protect code requires the clocks be
registered with clkdev. This was missing for sunxi_gates
type clocks.

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