clk: sunxi-ng: sun6i: Export video PLLs

The 2x outputs of the 2 video PLL clocks are directly used by the
HDMI controller block.

Export them so they can be referenced in the device tree.

Fixes: c6e6c96d ("clk: sunxi-ng: Add A31/A31s 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>