clk: imx: clk-imx8mn Fix nand and spi clock parent

The osc_24m is the clock-output-name and not the one that
is used as internal name reference from the strcmp. The clock
that use osc_24m, will not be able to reparent it as they should.
We need anyway register the osc_24m clock fixed factor in the clock
tree.

Fixes: 710c4ffb ("clk: imx: clk-imx8mn add gpmi nand clocks")
Fixes: 85b1c119 ("clk: imx: Add ECSPI to iMX8MN")
Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>