spl: Convert SYS_MMCSD_RAW_MODE_KERNEL_SECTOR to Kconfig

Falcon mode is very useful in improving boot speed. A question that
Falcon mode asks is "Where do I look for the kernel". With MMC boot
media, the correct answer is CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR.
The scope of this patch is to move this to Kconfig.

It is possible for a system to support Falcon mode from NOR but not
MMC. In that case, mmc_load_image_raw_os() would not be used. To
address this, conditionally compile mmc_load_image_raw_os() when
SPL_FALCON_BOOT_MMCSD, instead of SPL_OS_BOOT.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
[trini: Move spl_start_uboot to its own guard in spl_mmc.c, rerun migration]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/dra7xx_evm_defconfig b/configs/dra7xx_evm_defconfig
index d1aa91d..e96e2a7 100644
--- a/configs/dra7xx_evm_defconfig
+++ b/configs/dra7xx_evm_defconfig
@@ -34,6 +34,8 @@
 CONFIG_SPL_NAND_BASE=y
 CONFIG_SPL_DM_SPI_FLASH=y
 CONFIG_SPL_OS_BOOT=y
+CONFIG_SPL_FALCON_BOOT_MMCSD=y
+CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR=0x1700
 CONFIG_SPL_RAM_SUPPORT=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x40000