uboot-imx

mmc: fsl_esdhc: Add support to force VSELECT set

Some boards cannot do voltage negotiation but need to set the VSELECT
bit forcely to ensure it to work at 1.8V.

This commit adds CONFIG_SYS_FSL_ESDHC_FORCE_VSELECT flag for this use.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>