CONFIG_MACH_SPEAR300 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
SPEAr300
modulename: spear300.ko
configname: CONFIG_MACH_SPEAR300
Linux Kernel Configuration
└─>SPEAr300
In linux kernel since version 2.6.35 (release Date: 2010-08-01)
Supports ST SPEAr300 Machine