CONFIG_SOC_SAMA5D2 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

SAMA5D2 family

modulename: sama5d2.ko

configname: CONFIG_SOC_SAMA5D2

Linux Kernel Configuration
└─>AT91/Microchip SoCs
└─>SAMA5D2 family
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Select this if ou are using one of Microchip's SAMA5D2 family SoC.

source code:
drivers/clk/at91/