CONFIG_SIMDISK1_FILENAME is not available for thedefaultarchitecture x86.
Result is shown for architecture xtensa

Host filename for the second simulated device

configname: CONFIG_SIMDISK1_FILENAME

Linux Kernel Configuration
└─>Platform options
└─>Host filename for the second simulated device
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Another simulated disk in a host file for a buildroot-independent
storage.

depends
CONFIG_BLK_DEV_SIMDISK
CONFIG_BLK_DEV_SIMDISK_COUNT!1