CONFIG_PPC4xx_OCM is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

PPC4xx On Chip Memory (OCM) support

modulename: ocm.ko

configname: CONFIG_PPC4xx_OCM

Linux Kernel Configuration
└─>PPC4xx On Chip Memory (OCM) support
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Enable OCM support for PowerPC 4xx platforms with on chip memory,
OCM provides the fast place for memory access to improve performance.

source code:
arch/powerpc/platforms/4xx/ocm.c

depends
CONFIG_4xx