boards: nxp: frdm_mcxn947: add support for USDHC0

Add support for USDHC0 controller on FRDM_MCXN947 board. This support
was verified using the `tests/subsys/sd/sdmmc` and
`tests/subsys/sd/sdio` testcases. Note that this board does not ship
with the SD header (J12) populated by default, so the user must populate
one.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>