This change tries to fix the following problem:
- The board boots (to be more precise - ROM loads SPL) from a slow SPI-NOR
memory.
As a result the spl_boot_device() will return SPI-NOR as a boot device
(which is correct).
- The problem is that in 'falcon boot' the eMMC is used as a boot medium to
load kernel from its partition.
Calling spl_boot_device() will break things as it returns SPI-NOR device.
To fix this issue the new CONFIG_SPL_FORCE_MMC_BOOT Kconfig flag is
introduced to handle this special use case. By default it is not defined,
so there is no change in the legacy code flow.
Signed-off-by: Lukasz Majewski <lukma@denx.de>
772b55723b