media: video: tegra: Don't overwrite avp outbox

Before writing a new value in avp outbox register ensure the last
value written in it has been read by AVP. If AVP has not yet read
the current value in avp outbox register then wait until it is done.

Bug 1054421

Change-Id: Ie1f024969d9fcb87cf6f88b8ee3b557874eb310c
Signed-off-by: Sumit Bhattacharya <sumitb@nvidia.com>
Reviewed-on: http://git-master/r/139406
(cherry picked from commit ecd44726ca121df4697044f5e0398aa75106ff63)

Signed-off-by: Sumit Bhattacharya <sumitb@nvidia.com>
Change-Id: Ie01542d9ce27fff87d2a9fc5aec5d9310ed0583d
Reviewed-on: http://git-master/r/141227
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Niranjan Wartikar <nwartikar@nvidia.com>
Reviewed-by: Ravindra Lokhande <rlokhande@nvidia.com>
Reviewed-by: Scott Peterson <speterson@nvidia.com>
GVS: Gerrit_Virtual_Submit