intel/igc:fix repeated words in comments

Delete the redundant word 'frames'.
Signed-off-by: NJilin Yuan <yuanjilin@cdjrlc.com>
Signed-off-by: NTony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/igc/igc_mac.c

@@ -193,7 +193,7 @@ s32 igc_force_mac_fc(struct igc_hw *hw)
 	 *      1:  Rx flow control is enabled (we can receive pause
 	 *          frames but not send pause frames).
 	 *      2:  Tx flow control is enabled (we can send pause frames
-	 *          frames but we do not receive pause frames).
+	 *          but we do not receive pause frames).
 	 *      3:  Both Rx and TX flow control (symmetric) is enabled.
 	 *  other:  No other values should be possible at this point.
 	 */