CONFIG_DEBUG_MSM_UART3 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Kernel low-level debugging messages via MSM UART3

configname: CONFIG_DEBUG_MSM_UART3

Kernel low-level debugging port
└─>Kernel low-level debugging messages via MSM UART3
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Say Y here if you want the debug print routines to direct
their output to the third serial port on MSM devices.