clk: imx8m: drop clk_hw_set_parent for A53

The parent settings have been moved to dtsi, we no need to
set parent here. And clk_hw_set_parent will trigger lockdep warning,
because this api not have prepare_lock.

Reported-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>