model_106cx: don't blindly set Kconfig settings

The CPU_ADDR_BITS was being unconditionally set.
Don't do that.

Change-Id: Idbc63328fade8f5f05f7f46282139b86e6694989
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/169711
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
(cherry picked from commit 858f96d28d8d0aeffe58e1d4d1d559ad161aab66)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6535
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>