Fix comment

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2998 42af7a65-404d-4744-a932-0658087f49c3

arch/avr/src/at91uc3/at91uc3_wdt.h

@@ -66,7 +66,7 @@
 #define WDT_CTRL_KEY_SHIFT   (24)     /* Bits 24-31: Write protection key */
 #define WDT_CTRL_KEY_MASK    (0xff << WDT_CTRL_KEY_SHIFT)
 
-/* Clear Register Bit-field Definitions.  These registera have no bit fielda: "Writing
+/* Clear Register Bit-field Definitions.  These registers have no bit fields: "Writing
  * periodically any value to this field when the WDT is enabled, within the watchdog
  * time-out period, will prevent a watchdog reset."
  */