clk: imx8qm: fix usdhc2 clocks

Trying to bring up uSDHC2 the following error message was observed:

MMC:   imx8_clk_set_rate(Invalid clk ID #60)
imx8_clk_set_rate(Invalid clk ID #60)
usdhc@5b030000 - probe failed: -22

This commit fixes this by properly setting resp. clocks.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Max Krummenacher <max.krummenacher@toradex.com>