iwlwifi: fix a typo

We never have four chains, but let's fix the typo
while we noticed it. You count 0, 1, 2, 3, not
0, 1, 2, 4 :)

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -984,7 +984,7 @@ static u8 iwl_count_chain_bitmap(u32 chain_bitmap)
 	res = (chain_bitmap & BIT(0)) >> 0;
 	res += (chain_bitmap & BIT(1)) >> 1;
 	res += (chain_bitmap & BIT(2)) >> 2;
-	res += (chain_bitmap & BIT(4)) >> 4;
+	res += (chain_bitmap & BIT(3)) >> 3;
 	return res;
 }