diag: Add support for MSM8929 QPST string

MSM8929 is a new device. Add diag support for sending
appropriate model number for MSM8929 so that QPST
can display the appropriate string.

Change-Id: I4e92f5a114b542083178fdb8d68f95990f741bee
Signed-off-by: Mohit Aggarwal <maggarwa@codeaurora.org>