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 <[email protected]>
Signed-off-by: Rajashekhara, Sudhakar <[email protected]>
Signed-off-by: Lad, Prabhakar <[email protected]>
Signed-off-by: Hadli, Manjunath <[email protected]>