Remove tx-fastpath ref. to hardware-offloaded encapsulation.

The Mindspeed kernel does not have the upstream patch:

"net: Add support for hardware-offloaded encapsulation"

Remove references to it introduced by tx-fastpath patch. Verified this
change with Johannes Berg. Backports will presumably deal with this once
tx-fastpath arrives in linux-next.

Change-Id: If546ce7738c66e7e87e06b76267685e3f2f133c4
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 96dcf99..730acad 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2887,12 +2887,8 @@
 		 * fix it up in software before we handle anything else.
 		 */
 		if (skb->ip_summed == CHECKSUM_PARTIAL) {
-			if (skb->encapsulation)
-				skb_set_inner_transport_header(skb,
-							       skb_checksum_start_offset(skb));
-			else
-				skb_set_transport_header(skb,
-							 skb_checksum_start_offset(skb));
+			skb_set_transport_header(skb,
+						 skb_checksum_start_offset(skb));
 			if (skb_checksum_help(skb))
 				goto out_free;
 		}