msm: tsc: Fix buffer mode transaction handling

The VBIF is required for buffer mode transactions in
the TSC-CI. This change enables proper mapping of an ION handle
to the VBIF.

Change-Id: Ie2f7582dcc5bee0aa030a8a2beff9f9ceabb60ec
Signed-off-by: Anat Etzion-Fuchs <aetzion@codeaurora.org>