ssb: extif: add check for max value before setting watchdog register

Prevent the watchdog register on the extif core to be set to a too
high value.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/linux/ssb/ssb_driver_extif.h b/include/linux/ssb/ssb_driver_extif.h
index 2604efa..b618188 100644
--- a/include/linux/ssb/ssb_driver_extif.h
+++ b/include/linux/ssb/ssb_driver_extif.h
@@ -152,6 +152,7 @@
 /* watchdog */
 #define SSB_EXTIF_WATCHDOG_CLK		48000000	/* Hz */
 
+#define SSB_EXTIF_WATCHDOG_MAX_TIMER	((1 << 28) - 1)
 
 
 #ifdef CONFIG_SSB_DRIVER_EXTIF