x86/Kconfig: Add cmpxchg8b support back to Geode CPUs

An older cleanup of mine inadvertently removed geode-gx1 and geode-lx
from the list of CPUs that are known to support a working cmpxchg8b.

Fixes: 88a2b4ed ("x86/Kconfig: Rework CONFIG_X86_PAE dependency")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250226213714.4040853-2-arnd@kernel.org