clk: imx93: add SAI IPG clk

The clk topology is as below:
bus_aon_root------>\                  /--->SAI IPG
                    -->SAI LPCG gate-->
sai[x]_clk_root--->/                  \--->SAI MCLK

So use shared count as i.MX93 MU_B gate.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20220830033137.4149542-9-peng.fan@oss.nxp.com