backlight: max8831: Change brightness setting under System EDP constraints

backlight: max8831: Change brightness setting under System EDP constraints

Change backlight setting behavior to the following:
1) Compare requested brightness with available EDP states
2) Request the next higher EDP state from EDP manager
3) Set brightness to min(requested brightness, approved brightness)

Bug 1276795

Change-Id: I77ddc2f74bcd3e848bb8d4df59f524f871db7557
Signed-off-by: Daniel Solomon <daniels@nvidia.com>
Reviewed-on: http://git-master/r/222671
(cherry picked from commit 5a3e41592a9e41b9992f2f80437d7b7195f0fe24)
Reviewed-on: http://git-master/r/226777
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Karthik Ramakrishnan <karthikr@nvidia.com>
Tested-by: Karthik Ramakrishnan <karthikr@nvidia.com>
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>