da850/omap-l138: Make MMC and NOR support mutually exclusive

da850/omap-l138: Make MMC and NOR support mutually exclusive

On Logic PD Rev.3 DA850/OMAP-L138 EVM, NOR and MMC/SD cannot
work together. This patch enables the MMC/SD support only
when NOR support is disabled. NOR Flash identification works
even without this patch, but erase and write will have issues.

Tested-by: Christian Riesch <christian.riesch@omicron.at>
Signed-off-by: Rajashekhara, Sudhakar <sudhakar.raj@ti.com>
Signed-off-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Hadli, Manjunath <manjunath.hadli@ti.com>