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

CONFIG_IMX_HAVE_PLATFORM_MXC_MMC (not configurable)

modulename: platform-mxc-mmc.ko

configname: CONFIG_IMX_HAVE_PLATFORM_MXC_MMC

Linux Kernel Configuration
└─>IMX_HAVE_PLATFORM_MXC_MMC
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
source code:
arch/arm/mach-imx/devices/platform-mxc-mmc.c