The CONFIG_SPL_FORCE_MMC_BOOT config flag is not needed as its behavior
is the correct one in all cases; using spl_boot_device() instead of the
boot_device parameter will lead to inconsistency issues, for example,
when a board_boot_order() is defined. In fact, this is the reason the
parameter was introduced in the first place, in commit 2b1cdafa9f
("common: Pass the boot device into spl_boot_mode()").
This reverts commit 772b55723b.
Link: https://lists.denx.de/pipermail/u-boot/2020-April/405979.html
Signed-off-by: Harald Seiler <hws@denx.de>