arm64: dts: imx8mp-beacon-kit: Fix Stereo Audio on WM8962

The L/R clock needs to be controlled by the SAI3 instead of the
CODEC to properly achieve stereo sound. Doing this allows removes
the need for unnecessary clock manipulation to try to get the
CODEC's clock in sync with the SAI3 clock, since the CODEC can cope
with a wide variety of clock inputs.

Fixes: 161af16c ("arm64: dts: imx8mp-beacon-kit: Fix audio_pll2 clock")
Fixes: 69e2f37a ("arm64: dts: imx8mp-beacon-kit: Enable WM8962 Audio CODEC")
Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>