CONFIG_SOC_IMX5 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_SOC_IMX5 (not configurable)

modulename: cpu-imx5.ko

configname: CONFIG_SOC_IMX5

Linux Kernel Configuration
└─>Freescale i.MX support
└─>SOC_IMX5
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
/arch/arm/mach-imx/

depends
CONFIG_ARCH_MXC

is selected by
CONFIG_FEC_PTP