clk: imx6ul: retain early UART clocks during kernel init

Make sure to keep UART clocks enabled during kernel init if
earlyprintk or earlycon are active.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20230421115517.1940990-1-alexander.stein@ew.tq-group.com


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