msm: camera: Correct the reserve buffer logic in mctl_pp.

When the daemon asks to reserve a free buffer, get the
correct address by using the image mode to get to the
correct camera instance and populating the buffer address.

Change-Id: I23c6e00458562ef2b9880cbffe2d6a100de80ea1
Signed-off-by: Kevin Chan <ktchan@codeaurora.org>
Signed-off-by: Kiran Kumar H N <hurlisal@codeaurora.org>
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>