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

Palm Centro 685 (GSM)

configname: CONFIG_MACH_CENTRO

Linux Kernel Configuration
└─>Intel PXA2xx/PXA3xx Implementations
└─>Palm Centro 685 (GSM)
In linux kernel since version 2.6.33 (release Date: 2010-02-24)  
Say Y here if you intend to run this kernel on Palm Centro 685 (GSM)
smartphone.