net: qrtr: haven: Add svm device tree parsing

The secondary vm device tree will have a different format than the
primary vm. Try parsing the node as a secondary vm node if the
shared-buffer region does not exist.

Change-Id: I4dc65096a43a9f1d3b3baaa6fb87e6b08144830e
Signed-off-by: Chris Lew <clew@codeaurora.org>