IMXBSP-66 ARM64: dts: imx8ulp-evk: change the drive strength for usdhc pad

Hardware suggest to use Standard Drive Strength for USDHC pad to get a better
signal quality.

Reviewed-by: Sherry Sun <sherry.sun@nxp.com>
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>