CONFIG_MTD_AT91_DATAFLASH_CARD is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_MTD_AT91_DATAFLASH_CARD.
Result is shown for kernelversion 6.5.1

Enable DataFlash Card support

configname: CONFIG_MTD_AT91_DATAFLASH_CARD

Linux Kernel Configuration
└─>Atmel Non-DT world
└─>Enable DataFlash Card support
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
Enable support for the DataFlash card.