clk: imx: imx8ulp: keep MU0_B clock enabled always

Keep the A35<->M33 MU0_B clock enabled always for low power
communication.

Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20230331063814.2462059-4-peng.fan@oss.nxp.com


Signed-off-by: Abel Vesa <abel.vesa@linaro.org>