arm64: dts: imx8mp: don't initialize audio clocks from CCM node

The audio clocks should be intitialized to the correct rate by the subsystem
using them. There is no need to always initialize them from the CCM node
assigned-clocks property. This way boards using the audio clocks in a non-
standard way can change them without first duplicating the CCM clock
setup.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>