dt-bindings: clock: Add Marvell MMP Audio Clock Controller binding

This describes the bindings for a controller that generates master and bit
clocks for the I2S interface.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Link: https://lkml.kernel.org/r/20200519224151.2074597-13-lkundrak@v3.sk
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>