CONFIG_MACH_QSD8X50A_ST1_5 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

QSD8x50A ST1.5

configname: CONFIG_MACH_QSD8X50A_ST1_5

Linux Kernel Configuration
└─>Qualcomm MSM Board Type
└─>QSD8x50A ST1.5
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
Support for the Qualcomm ST1.5.