arm64: dts: imx8mm: Drop sd-vsel-gpios from i.MX8M Mini Verdin SoM

The VSELECT pin is configured as MX8MM_IOMUXC_GPIO1_IO04_USDHC2_VSELECT
and not as a GPIO, drop the bogus sd-vsel-gpios property as the eSDHC
block handles the VSELECT pin on its own.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>