drivers: watchdog: rti_wdt: allow device specific timeout configuration

The source of the timeout value for an inactive watchdog is now evaluated
in the following order:
1. "timeout-sec" from the Device Tree (per-watchdog)
2. Module parameter (global)
3. Default value (60 s) (global)

This reordering ensures that device-specific configuration takes precedence
over global defaults, improving flexibility for systems with multiple watchdogs.

Signed-off-by: Peter Galka <peter.galka@wago.com>

arch/arm64/boot/dts/ti/k3-am62x-pfc.dtsi

@@ -886,6 +886,14 @@
 	};
 };
 
+/*
+ * This system watchdog is reserved for internal use and is not user-configurable.
+ * It must not be modified or deleted to ensure consistent behavior!
+ */
+&main_rti1 {    // watchdog@e010000
+    timeout-sec = <120>;
+};
+
 /*
  * AM6232 does not have main_rti2, main_rti3, and main_rti15
  * https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1218039/am623-stuck-in-sd-card-after-boot-up

drivers/watchdog/rti_wdt.c

@@ -335,7 +335,9 @@ static int rti_wdt_probe(struct platform_device *pdev)
 		memunmap(vaddr);
 	}
 
-	watchdog_init_timeout(wdd, heartbeat, dev);
+	// grab timeout from DTS first
+	wdd->timeout = heartbeat;
+	watchdog_init_timeout(wdd, 0, dev);
 
 	ret = watchdog_register_device(wdd);
 	if (ret) {