msm: wfd: Fix WARN_ON() when initing vb2_queue

As of kernel 3.10, initing vb2_queue without specifying how timestamps
are generated triggers a WARN_ON.  Specify the timestamp so that the vb2
framework doesn't complain.

Change-Id: I467e8263901158c9dc8317b8b8581d51b515a2b7
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>
CRs-Fixed: 588440