CONFIG_MACH_U300 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

U300

modulename: gpio-u300.ko

configname: CONFIG_MACH_U300

Linux Kernel Configuration
└─>ST-Ericsson AB U300/U330/U335/U365 Platform
└─>U300
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
source code:
drivers/gpio/gpio-u300.c