CONFIG_SOC_AT91SAM9263 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

AT91SAM9263

modulename: at91sam9263.ko

configname: CONFIG_SOC_AT91SAM9263

Linux Kernel Configuration
└─>Atmel AT91 System-on-Chip
└─>AT91SAM9263
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
arch/arm/mach-at91/at91sam9263.c