clk: zte: add audio clocks for zx296718

The audio related clock support is missing from the existing zx296718
clock driver.  Let's add it, so that the upstream ZX SPDIF driver can
work for HDMI audio support.

Signed-off-by: Jun Nie <jun.nie@linaro.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
[sboyd@codeaurora.org: Staticize some more structures]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>