ARM: dts: sun6i: rename clock node names to clk@N

Device tree naming conventions state that node names should match
node function. Change fully functioning clock nodes to match and
add clock-output-names to all sunxi clock nodes.

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