watchdog: Fix typo in Kconfig

Correct spelling "overidden" to "overridden" in
drivers/watchdog/Kconfig

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/Kconfig

@@ -1098,7 +1098,7 @@ config BOOKE_WDT_DEFAULT_TIMEOUT
 	  For Freescale Book-E processors, this is a number between 0 and 63.
 	  For other Book-E processors, this is a number between 0 and 3.
 
-	  The value can be overidden by the wdt_period command-line parameter.
+	  The value can be overridden by the wdt_period command-line parameter.
 
 # PPC64 Architecture