ARM: dts: imx7d-pico: Pass 'no-1-8-v' property to the eMMC

Currently the following eMMC error is seen:

mmc1: mmc_select_hs200 failed, error -74

On imx7d-pico the eMMC VCCQ is fixed at 3.15V, so pass the 'no-1-8-v'
property to properly describe that 1.8V operation is not possible.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>