arch/x86/Kconfig: Add deprecation warnings for LATE_CBMEM_INIT

The deprecation of late (post-romstage) CBMEM initialization was
announced in this blog post:

There are two warnings:
* In LATE_CBMEM_INIT's help text, I've added a multi-line warning, that
  aims to explain the problem.
* In src/mainboard/Kconfig (just below the mainboard selection), there's
  a warning which points the user at LATE_CBMEM_INIT, if such a board is

Also update the function that needs to be implemented, as pointed out by
Keith Hui and Kyösti Mälkki.

Change-Id: I2d21a6ab2fc2811d44fc4febb05841bb2f8d1857
Signed-off-by: Jonathan Neuschäfer <>
Tested-by: build bot (Jenkins) <>
Reviewed-by: Kyösti Mälkki <>
2 files changed