iwlwifi: replace magic constants with define

use IWL_CCK_RATES_MASK and IWL_OFDM_RATES_MASK instead of
their values directly.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
cc: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.c b/drivers/net/wireless/iwlwifi/iwl-agn.c
index 03acad2..ab599a9 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn.c
@@ -466,9 +466,9 @@
 
 	/* Set rate mask*/
 	if (priv->staging_rxon.flags & RXON_FLG_BAND_24G_MSK)
-		rate_mask = priv->active_rate_basic & 0xF;
+		rate_mask = priv->active_rate_basic & IWL_CCK_RATES_MASK;
 	else
-		rate_mask = priv->active_rate_basic & 0xFF0;
+		rate_mask = priv->active_rate_basic & IWL_OFDM_RATES_MASK;
 
 	/* Find lowest valid rate */
 	for (i = IWL_RATE_1M_INDEX; i != IWL_RATE_INVALID;