diag: Add support for MSM8916 QPST string

MSM8916 is a new device. Add diag support for sending
appropriate model number for MSM8916 so that QPST
can display the appropriate string.

Change-Id: Ie19cd3893ebbf8f9419a4a4b40833c51553ae527
Signed-off-by: Mohit Aggarwal <maggarwa@codeaurora.org>