UBUNTU: SAUCE: ath10k: fix the wifi speed issue for kill 1535

BugLink: http://bugs.launchpad.net/bugs/1692836

The fix is suggested by Qualcomm, and it helps to fix the network speed
issue.
Ath10k driver changed a lot after 4.4 kernel, so this fix can't
applied on other kernels than 4.4. We need to figure out other way for
kernels after Xenial.

Without the patch, the 5GHz network speed is pretty low
   11n
      0.0-120.1 sec 271 MBytes 18.9 Mbits/sec
   11AC
      0.0-120.2 sec 141 MBytes 9.86 Mbits/sec

After applied the patch
   11n
      0.0-120.0 sec 2.04 GBytes 146 Mbits/sec
   11AC
      0.0-120.0 sec 1.17 GBytes 83.6 Mbits/sec
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/wireless/ath/ath10k/mac.c

@@ -3637,6 +3637,8 @@ static void ath10k_tx(struct ieee80211_hw *hw,
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 	__le16 fc = hdr->frame_control;
 
+	skb_orphan(skb);
+
 	/* We should disable CCK RATE due to P2P */
 	if (info->flags & IEEE80211_TX_CTL_NO_CCK_RATE)
 		ath10k_dbg(ar, ATH10K_DBG_MAC, "IEEE80211_TX_CTL_NO_CCK_RATE\n");