dfc: TCP pure acks

Detects TCP pure acks so they can be put in the dedicated TX queues
even if they contain various options.

Change-Id: I6a9b714ccb58616ff49a150467d33a348d88ec64
Acked-by: Weiyi Chen <weiyic@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>