Don't trigger device notifications when Steam Deck backlight changes

src/hidapi/SDL_hidapi.c

@@ -416,7 +416,10 @@ HIDAPI_UpdateDiscovery()
                     const char *action = NULL;
                     action = usyms->udev_device_get_action(pUdevDevice);
                     if (!action || SDL_strcmp(action, "add") == 0 || SDL_strcmp(action, "remove") == 0) {
-                        ++SDL_HIDAPI_discovery.m_unDeviceChangeCounter;
+                        const char *subsystem = usyms->udev_device_get_subsystem(pUdevDevice);
+                        if (!subsystem || SDL_strcmp(subsystem, "backlight") != 0) {
+                            ++SDL_HIDAPI_discovery.m_unDeviceChangeCounter;
+                        }
                     }
                     usyms->udev_device_unref(pUdevDevice);
                 }