iwlagn: workaround bug crashing some APs

This patch reverts commit 9b76883 which
was introduced in 2.6.38-rc1.  It works around a problem where the iwlagn
driver stimulates a bug crashing (requiring power cycle to recover) some
APs under heavy traffic.

CC: stable@kernel.org #2.6.39, #3.0.0 #3.1.0
Signed-off-by: Don Fry <donald.h.fry@intel.com>
SIgned-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -2140,7 +2140,12 @@ static int iwl_mac_setup_register(struct iwl_priv *priv,
 		    IEEE80211_HW_SPECTRUM_MGMT |
 		    IEEE80211_HW_REPORTS_TX_ACK_STATUS;
 
+	/*
+	 * Including the following line will crash some AP's.  This
+	 * workaround removes the stimulus which causes the crash until
+	 * the AP software can be fixed.
 	hw->max_tx_aggregation_subframes = LINK_QUAL_AGG_FRAME_LIMIT_DEF;
+	 */
 
 	hw->flags |= IEEE80211_HW_SUPPORTS_PS |
 		     IEEE80211_HW_SUPPORTS_DYNAMIC_PS;