msm: vidc: Change control type of ENABLE_INITIAL_QP

V4L2_CID_MPEG_VIDC_VIDEO_ENABLE_INITIAL_QP should be of type BITMASK, as
the client sets a bitmask of the frame specific QPs that it wishes to
initialise.

Change-Id: I07da8c7c86a4e87ae89eec0044f0b3459e524e42
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>