Added SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION and
SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION to Kconfig.

Due to SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION being moved to
Kconfig the board defconfigs for db-88f6820-gp_defconfig
kc1_defconfig and sniper_defconfig need to be updated.
Signed-off-by: NDalon Westergreen <dwesterg@gmail.com>