msm: vidc: add ion_handle checking before mapping buffers

Compare ion handles in driver instead of matching fds
to check if a buffer is already mapped or not.

Bug: 28747768

Change-Id: Ifd18d8689351c4a6a22c988d359fb413be19e142
Signed-off-by: Ashray Kulkarni <ashrayk@codeaurora.org>
Signed-off-by: Praveen Chavan <pchavan@codeaurora.org>
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>
Signed-off-by: Arun Menon <avmenon@codeaurora.org>