clk: sunxi-ng: Add hardware dependency

The sunxi-ng clock driver is useless for other architectures.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>