msm: vidc: Re-add example for qcom,buffer-type-tz-usage-table

Re-add example for qcom,buffer-type-tz-usage-table in the DT
documentation.  This was accidentally deleted as part of an earlier
commit.

Change-Id: If8744b54683ac7fb4c02ad12275fa145f2b07949
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>