mdss: Add newline to VSYNC timestamp for mdp3 driver

This makes sure that the userspace correctly interprets the end
of the vsync timestamp.

CRs-Fixed: 639039
Change-Id: I8a0810283a42a9c39a3c8fe36b862bbfd3ecdbea
Signed-off-by: Shivaraj Shetty <shivaraj@codeaurora.org>