CONFIG_DEBUG_AT91_SAMA5D2_UART1 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Kernel low-level debugging on SAMA5D2 UART1

configname: CONFIG_DEBUG_AT91_SAMA5D2_UART1

Kernel low-level debugging port
└─>Kernel low-level debugging on SAMA5D2 UART1
In linux kernel since version 4.1 (release Date: 2015-06-21)  
Say Y here if you want kernel low-level debugging support
on the UART1 port of sama5d2.