diag: Add support for header untagging

This patch provides the support for segregate different PD data onto
separate buffers and then onto its own data stream based on received
diag private id header from the peripheral data packets.
This patch adds a new feature mask supporting the feature and
a new IOCTL querying the support of the feature.

CRs-Fixed: 1112307
Change-Id: Id76e718f83e09defc221f9ee169d4676d8e57d8a
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>