CONFIG_ARCH_OMAP2PLUS is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

TI OMAP2/3/4/5 SoCs with device tree support

configname: CONFIG_ARCH_OMAP2PLUS

Linux Kernel Configuration
└─>TI OMAP2/3/4/5 SoCs with device tree support
In linux kernel since version 2.6.34 (release Date: 2010-05-16)  
Systems based on OMAP2, OMAP3, OMAP4 or OMAP5