CONFIG_SA1100_PLEB is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

PLEB

modulename: pleb.ko

configname: CONFIG_SA1100_PLEB

Linux Kernel Configuration
└─>SA11x0 Implementations
└─>PLEB
In linux kernel since version 2.6.12  
Say Y here if you are using version 1 of the Portable Linux
Embedded Board (also known as PLEB).
See <http://www.disy.cse.unsw.edu.au/Hardware/PLEB/>
for more information.

source code:
arch/arm/mach-sa1100/pleb.c