arm: tegra14x: bb: override DSR when EMC floor is set

arm: tegra14x: bb: override DSR when EMC floor is set

Dynamic Self Refresh (DSR) feature in EMC affects BBC's latency.
Override DSR when min EMC frequency is set and enable it
when BBC becomes idle.

Change-Id: I8554910c62bc35a2887e6ed2e49b3240944028dc
Signed-off-by: Vinayak Pane <vpane@nvidia.com>
Reviewed-on: http://git-master/r/224045
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Steve Lin <stlin@nvidia.com>