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

CONFIG_MSM_GPIOMUX (not configurable)

configname: CONFIG_MSM_GPIOMUX

Linux Kernel Configuration
└─>MSM_GPIOMUX
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
depends
CONFIG_ARCH_MSM