atmel-samd: Fix converting watchdog seconds to cycles

It's intended that the actual timeout always be at least the requested
timeout.  However, due to multiplying by the wrong factor to get from
seconds to cycles, a timeout request of e.g., 8.1s (which is less than
8.192s) would give an actual timeout of 8, not 16 as it should.

Author: jepler

ports/atmel-samd/common-hal/watchdog/WatchDogTimer.c

@@ -70,7 +70,7 @@ void setup_wdt(watchdog_watchdogtimer_obj_t *self, int setting) {
 }
 
 void common_hal_watchdog_set_timeout(watchdog_watchdogtimer_obj_t *self, mp_float_t new_timeout) {
-    int wdt_cycles = (int)(new_timeout * 1000);
+    int wdt_cycles = (int)(new_timeout * 1024);
     if (wdt_cycles < 8) {
         wdt_cycles = 8;
     }