CONFIG_ARCH_OMAP24XX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

OMAP24xx Based System

modulename: sleep24xx.ko

configname: CONFIG_ARCH_OMAP24XX

Linux Kernel Configuration
└─>OMAP24xx Based System
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
source code:
/arch/arm/mach-omap2/

is selected by
CONFIG_MACH_OMAP_2430SDP