CONFIG_MACH_U300_SINGLE_RAM is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Single RAM

configname: CONFIG_MACH_U300_SINGLE_RAM

Memory configuration
└─>Single RAM
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
Select this if you want support for Single RAM phones.