iwlegacy: enable only rfkill interrupt when device is down

Add two below iwlwifi commits to iwlegacy:

commit 554d1d027b19265c4aa3f718b3126d2b86e09a08
Author: Stanislaw Gruszka <sgruszka@redhat.com>
Date:   Thu Dec 23 12:38:21 2010 +0100

    iwlagn: enable only rfkill interrupt when device is down

commit 3dd823e6b86407aed1a025041d8f1df77e43a9c8
Author: Don Fry <donald.h.fry@intel.com>
Date:   Sun Feb 6 09:29:45 2011 -0800

    iwlagn: Re-enable RF_KILL interrupt when down

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlegacy/iwl-helpers.h b/drivers/net/wireless/iwlegacy/iwl-helpers.h
index 02132e7..a6effda 100644
--- a/drivers/net/wireless/iwlegacy/iwl-helpers.h
+++ b/drivers/net/wireless/iwlegacy/iwl-helpers.h
@@ -149,6 +149,12 @@
 	IWL_DEBUG_ISR(priv, "Disabled interrupts\n");
 }
 
+static inline void iwl_legacy_enable_rfkill_int(struct iwl_priv *priv)
+{
+	IWL_DEBUG_ISR(priv, "Enabling rfkill interrupt\n");
+	iwl_write32(priv, CSR_INT_MASK, CSR_INT_BIT_RF_KILL);
+}
+
 static inline void iwl_legacy_enable_interrupts(struct iwl_priv *priv)
 {
 	IWL_DEBUG_ISR(priv, "Enabling interrupts\n");