Merge branch '2021-12-01-Kconfig-migrations' into next

- Finish converting CONFIG_USE_BOOTCOMMAND, CONFIG_BOOTCOMMAND,
  CONFIG_RAMBOOTCOMMAND, CONFIG_NFSBOOTCOMMAND, all of
  CONFIG_SYS_[BO]R[0-7]_PRELIM, CONFIG_FSL_DDR_BIST and
  CONFIG_FSL_DDR_INTERACTIVE.