video: tegra: dp: eDP/miniDP support

video: tegra: dp: eDP/miniDP support

To add a support for an internal eDP panel or an external DP
monitor

- reduce the HPD waiting time to reasonable
- fix Alternate Scrambler Reset To 0xFFFE setting to support an
  external DP monitor
- fix unplugged eDP/miniDP display at boot time blocking detection
  of the HDMI display
- disable dpaux clock and pad power when no eDP panel or external
  monitor connected at boot time

Note: It works with the eDP panel or the monitor connected only at
      boot time.  No run-time hot plug support yet.
Note2: Reposting due the Gerrit bug.

bug 1409738

Change-Id: I81b8bab8881a6d849d97562deabd16fe794ff812
Signed-off-by: Sungwook Kim <sungwookk@nvidia.com>
Reviewed-on: http://git-master/r/405512
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Jon Mayo <jmayo@nvidia.com>