video: tegra: host: Support external syncpt cbs

video: tegra: host: Support external syncpt cbs

This far the nvhost driver has published interface for waiting
syncpoint values synchronously, however, we have need to do similar
waiting asynchronously (i.e. trigger event when certain syncpoint
value has been reached). This patch adds public function
nvhost_intr_register_notifier() that allows registering callbacks.

Change-Id: I3e8a12fad229b264a2ace5bb7f4726e17c90f112
Signed-off-by: Arto Merilainen <amerilainen@nvidia.com>
Reviewed-on: http://git-master/r/378342
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>