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

CONFIG_SPI_ETRAX_SSER (not configurable)

configname: CONFIG_SPI_ETRAX_SSER

Linux Kernel Configuration
└─>SPI_ETRAX_SSER
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
This enables using an synchronous serial (sser) port as a
SPI master controller on Axis ETRAX FS and later. The
driver can be configured to use any sser port.