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

CONFIG_ARCH_SHMOBILE (not configurable)

configname: CONFIG_ARCH_SHMOBILE

Linux Kernel Configuration
└─>ARCH_SHMOBILE
In linux kernel since version 2.6.30 (release Date: 2009-06-09)  
selects
CONFIG_ZONE_DMA