msm: camera: Remove usage of redundant variable.

When a diverted frame is returned from userspace, use the instance
handle present in the frame, if availabe. Otherwise fall back to
the image mode. We dont need to use the field 'path' since it shall
be deprecated soon.

Change-Id: I65d9edd9456d06fe2cc0d02e7c389efe6157447c
Signed-off-by: Kiran Kumar H N <hurlisal@codeaurora.org>