CONFIG_PMB is not available for thedefaultarchitecture x86.
Result is shown for architecture sh

PMB

modulename: pmb.ko

configname: CONFIG_PMB

PMB handling type
└─>PMB
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
If you say Y here, physical addressing will be extended to
32-bits through the SH-4A PMB. If this is not set, legacy
29-bit physical addressing will be used.

source code:
arch/sh/mm/pmb.c