CONFIG_SOC_MT7620 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

MT7620/8

modulename: mt7620.ko

configname: CONFIG_SOC_MT7620

Ralink SoC selection
└─>MT7620/8
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
/arch/mips/ralink/mt7620.c
is selected by
CONFIG_PINCTRL_MT7620