CONFIG_PXA3xx is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_PXA3xx (not configurable)

modulename: mfp-pxa3xx.ko

and/or

clk-pxa3xx.ko

and/or

mfp.ko

and/or

pxa3xx-cpufreq.ko

configname: CONFIG_PXA3xx

Linux Kernel Configuration
└─>PXA2xx/PXA3xx-based
└─>PXA3xx
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
Select code specific to PXA3xx variants

source code:
/arch/arm/mach-pxa/
selects
CONFIG_CPU_XSC3

depends
CONFIG_ARCH_PXA

is selected by
CONFIG_KEYBOARD_PXA27x