doxygen: RETURNS: -> @return

Previous comment style used RETRURNS:, use @return to comply
with javadoc style.

Change-Id: Ib1dffd92da1d97d60063ec5309b08049828f6661
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/drivers/timer/i8253.c b/drivers/timer/i8253.c
index 0a4052a..677a26e 100644
--- a/drivers/timer/i8253.c
+++ b/drivers/timer/i8253.c
@@ -148,7 +148,7 @@
  *
  * This routine reads the 16 bit value from the i8253 counter register.
  *
- * RETURNS: counter register's 16 bit value
+ * @return counter register's 16 bit value
  *
  * \NOMANUAL
  */
@@ -176,7 +176,7 @@
  * This routine sets the 16 bit value from which the i8253 timer will
  * decrement and sets that counter register to its value.
  *
- * RETURNS: N/A
+ * @return N/A
  *
  * \NOMANUAL
  */
@@ -198,7 +198,7 @@
  *
  * This routine sets the i8253 to fire on a periodic basis.
  *
- * RETURNS: N/A
+ * @return N/A
  *
  * \NOMANUAL
  */
@@ -218,7 +218,7 @@
  *
  * This routine sets the i8253 to fire once only.
  *
- * RETURNS: N/A
+ * @return N/A
  *
  * \NOMANUAL
  */
@@ -239,7 +239,7 @@
  * This routine handles the system clock periodic tick interrupt.  A TICK_EVENT
  * event is pushed onto the microkernel stack.
  *
- * RETURNS: N/A
+ * @return N/A
  *
  * \NOMANUAL
  */
@@ -316,7 +316,7 @@
  * value (the higher the tick frequency), the more elapsed ticks during a
  * "tickless idle".
  *
- * RETURNS: N/A
+ * @return N/A
  *
  * \NOMANUAL
  */
@@ -332,7 +332,7 @@
  *
  * _i8253TicklessIdleSkew -
  *
- * RETURNS: N/A
+ * @return N/A
  *
  * \NOMANUAL
  */
@@ -413,7 +413,7 @@
  *
  * Called in _IntEnt()
  *
- * RETURNS: N/A
+ * @return N/A
  */
 
 void _timer_idle_exit(void)
@@ -473,7 +473,7 @@
  * This routine is used to program the PIT to deliver interrupts at the
  * rate specified via the 'sys_clock_us_per_tick' global variable.
  *
- * RETURNS: N/A
+ * @return N/A
  */
 
 void timer_driver(int priority /* priority parameter ignored by this driver */
@@ -507,7 +507,7 @@
  *
  * This routine returns the current time in terms of timer hardware clock cycles.
  *
- * RETURNS: up counter of elapsed clock cycles
+ * @return up counter of elapsed clock cycles
  */
 
 uint32_t timer_read(void)
@@ -563,7 +563,7 @@
  * This routine simply disables the PIT counter such that interrupts are no
  * longer delivered.
  *
- * RETURNS: N/A
+ * @return N/A
  */
 
 void timer_disable(void)