diag: Add support for header untagging

This patch provides the support to segregate different PD data
received on DATA channel onto separate buffers and then onto
its own data stream based on received diag private id header
in the peripheral data packet header.
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>