msm: mdss: modify BW overhead and compression ratio related logic

As per the new qos strategy, overhead fudge factors are not needed and
thus remove related logic. Also as per the new qos implementation,
user-space program is responsible to passing on compression ratio when
they setup the pipeline. So cleanup current driver logic which makes
decision based on data path.

Change-Id: I3d4f7ab3749b5b8595ea322a0b5b25ba3187b660
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>