CONFIG_ETRAX_AXISFLASHMAP is not available for thedefaultarchitecture x86.
Result is shown for architecture cris

Axis flash-map support

modulename: axisflashmap.ko

and/or

head.ko

configname: CONFIG_ETRAX_AXISFLASHMAP

Linux Kernel Configuration
└─>Axis flash-map support
In linux kernel since version 2.6.12  
This option enables MTD mapping of flash devices. Needed to use
flash memories. If unsure, say Y.

source code:
arch/cris/arch-v10/drivers/axisflashmap.c