ARM: da850-evm: Disable SYS_MMCSD_RAW_MODE_USE_SECTOR

The da850-evm doesn't have the boot pins configured in a way
to make MMC/SD booting an option, and MMC/SD support is not
enabled in SPL.  Therefore, there is no need to support raw mode
mmc/sd support in SPL.

This patch disables CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR

Signed-off-by: Adam Ford <aford173@gmail.com>