CONFIG_SOC_AM33XX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

AM33XX support

configname: CONFIG_SOC_AM33XX

Linux Kernel Configuration
└─>TI OMAP2/3/4 Specific Features
└─>AM33XX support
In linux kernel since version 3.1 (release Date: 2011-10-24)  

is selected by
CONFIG_TI_CPSW