MLK-21484-4: ASoC: fsl_sai: ensure clk not in use prior set_mclk_rate

MLK-21484-4: ASoC: fsl_sai: ensure clk not in use prior set_mclk_rate

On recent kernels clks which are marked with CLK_SET_RATE_GATE are
"protected" against further changes at clk_prepare time, including clk
set_parent and set_rate. See commit 9461f7b33d11 ("clk: fix
CLK_SET_RATE_GATE with clock rate protection"). The current fsl_sai
implementation ensures the clock is not in use prior set_parent,
extend this for set_rate also by moving if (sai->mclk_streams == 0)
outside fsl_sai_set_mclk_rate(). Aside of this avoid changing rate and
parent for BUS clk.

Signed-off-by: Viorel Suman <viorel.suman@nxp.com>