CONFIG_GPTMR0_CLOCKSOURCE is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin

GPTimer0

configname: CONFIG_GPTMR0_CLOCKSOURCE

Linux Kernel Configuration
└─>Blackfin Processor Options
└─>Board customizations
└─>Clock source
└─>GPTimer0
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  

depends
CONFIG_GENERIC_CLOCKEVENTS
NOT CONFIG_TICKSOURCE_GPTMR0