msm: vidc: Return timestamps correctly back to the client

Propagate the timestamp client provides on the OUTPUT port to the
CAPTURE port.  Additionally, use kernel provided functions to convert
the timeval struct to a 64 bit value rather than requiring the clients
to set the timestamp within the tv_usec field.

Change-Id: I19b8b953c837199019d7370f8bf3afec88a0d00d
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>
Signed-off-by: Vinay Kalia <vkalia@codeaurora.org>