video: tegra: host: Pin each gather only once

Pin each gather only once. For each gather pinned, we copy the
acquired address to the rest of the gathers with the same memory
handle.

Change-Id: I47442cd5a167042b12a7fb4760a7ef0b83bdb9bd
Signed-off-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-on: http://git-master/r/139301
Reviewed-by: Juha Tukkinen <jtukkinen@nvidia.com>
Tested-by: Juha Tukkinen <jtukkinen@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User