default or selected kernelversion does not have config value CONFIG_TANGOX_WATCHDOG.
Result is shown for kernelversion 6.9.9

Sigma Designs SMP86xx/SMP87xx watchdog

modulename: tangox_wdt.ko

configname: CONFIG_TANGOX_WATCHDOG

Linux Kernel Configuration
└─>Device Drivers
└─>Watchdog Timer Support
└─>Sigma Designs SMP86xx/SMP87xx watchdog
In linux kernel since version 4.1 (release Date: 2015-06-21)  
Support for the watchdog in Sigma Designs SMP86xx (tango3)
and SMP87xx (tango4) family chips.

This driver can be built as a module. The module name is tangox_wdt.

source code:

depends
CONFIG_HAS_IOMEM
CONFIG_WATCHDOG
CONFIG_ARCH_TANGO or CONFIG_COMPILE_TEST