arm, at91, wdt: make timeout configurable

make the HW WDT timeout configurable through the define
CONFIG_AT91_HW_WDT_TIMEOUT.

Signed-off-by: Heiko Schocher <hs@denx.de>

README

@@ -1257,6 +1257,9 @@ The following options need to be configured:
 		SoC, then define this variable and provide board
 		specific code for the "hw_watchdog_reset" function.
 
+		CONFIG_AT91_HW_WDT_TIMEOUT
+		specify the timeout in seconds. default 2 seconds.
+
 - U-Boot Version:
 		CONFIG_VERSION_VARIABLE
 		If this variable is defined, an environment variable

drivers/watchdog/at91sam9_wdt.c

@@ -30,7 +30,11 @@
 #define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
 
 /* Hardware timeout in seconds */
+#if !defined(CONFIG_AT91_HW_WDT_TIMEOUT)
 #define WDT_HW_TIMEOUT 2
+#else
+#define WDT_HW_TIMEOUT CONFIG_AT91_HW_WDT_TIMEOUT
+#endif
 
 /*
  * Set the watchdog time interval in 1/256Hz (write-once)