msm: vidc: remove redundant init_completion() calls

Video driver is doing init_completion() for all completion
events in msm_vidc_initialize_core() and msm_vidc_open().
So there is no need of calling init_completion() again before
waiting for completion event and hence remove them.

Change-Id: Iedd9c4c0763c29b26e91e261d9a8d0e4e24b7bb2
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>
Signed-off-by: Paras Nagda <pnagda@codeaurora.org>