msm: msm_bus: Change priority overrides based on master configuration

When BIMC master enables BKE (in limiter mode), priority override
should be disabled since master is getting limited bandwidth.
However when BKE is disabled, make sure priority overrides are enabled
if master is in fixed mode.
Also enable the bke bit as part of switching QOS modes.

Change-Id: I318b3542f3f5da5685d5641701e0b6c8fc64732c
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>