CONFIG_44x is not available for thedefaultarchitecture x86.
Result is shown for architecture ppc

44x

modulename: 44x_mmu.ko

and/or

ibm44x_common.ko

and/or

ppc4xx_pic.ko

configname: CONFIG_44x

Processor Type
└─>44x
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
source code:
arch/ppc/mm/44x_mmu.c

is selected by
CONFIG_MTD_NAND_NDFC