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

Cardbus support

modulename: bios.ko

configname: CONFIG_ETRAX_CARDBUS

Linux Kernel Configuration
└─>Cardbus support
In linux kernel since version 2.6.13 (release Date: 2005-08-28)  
Enabled the ETRAX Cardbus driver.

source code: