efi-urgent-for-v5.10-rc5

- revert efivarfs kmemleak fix again - it was a false positive;
- make CONFIG_EFI_EARLYCON depend on CONFIG_EFI explicitly so it does not
  pull in other dependencies unnecessarily if CONFIG_EFI is not set
- defer attempts to load SSDT overrides from EFI vars until after the
  efivar layer is up.