msm: ipa: add a bit for tethering metadata

Assert the qmap reserved bit for tethering metadata register
to be able to filter tethered vs embedded traffic on IPA.

Change-Id: Id87156176091e52a88927b24f86942e060f341bd
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>