msm: camera: isp: Fix completion variable initialization

Initialize completion variable before cdm submit otherwise it can lead
to completion signaling before initializing completion variable. If
completion is signaled before init, it can lead wait time out or system
error.

Change-Id: I10a04390ff007ca9e2c7f72a5f908f7397a2780d
Signed-off-by: Tony Lijo Jose <tjose@codeaurora.org>