msm: camera: Add support for instance handle based buffer lookup.

Currently when VFE requests for a free buffer, we search based
on the image mode sent from VFE. In some cases, there can be
multiple instances with the same image mode. This means the
buffer lookup logic has to take into consideration other
parameters like current usecase, vfe operation mode etc.
To ease this, add support for buffer lookup based on
the instance handle. The instance handle contains information
about where to get the buffer from. So the buffer lookup
logic does not have to know about other details. The instance
handle is decided when the user sets the format for a particular
instance. It is passed on to the VFE during AXI configuration.
VFE stores this and sends it whenever it requests for a free
buffer for a particular output.
Keep the current image_mode based buffer lookup logic for
legacy targets.

Change-Id: I78c3db77ac4014365c9866ff780ec71ac4c7ff87
Signed-off-by: Kiran Kumar H N <hurlisal@codeaurora.org>