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

CONFIG_MXS_HAVE_PLATFORM_MXS_MMC (not configurable)

modulename: platform-mxs-mmc.ko

configname: CONFIG_MXS_HAVE_PLATFORM_MXS_MMC

Linux Kernel Configuration
└─>MXS_HAVE_PLATFORM_MXS_MMC
In linux kernel since version 2.6.39 (release Date: 2011-05-18)  
source code:
arch/arm/mach-mxs/devices/platform-mxs-mmc.c