mailbox: Add snapshot of MSM QMP driver

This snapshot is taken as of msm-4.14 'commit <67942dbf2187>
("Merge "net: netfilter: IRC DCC for private clients"")'.

In addition change copyrights to SPDX format.

Change-Id: I93381a6515263d1df949d93c9e158fd373a1d003
Signed-off-by: Chris Lew <clew@codeaurora.org>