video: tegra: dc: get default mode from EDID

video: tegra: dc: get default mode from EDID

Override hard-coded default HDMI mode with the preferred mode
obtained from EDID read. Since the preferred mode is obtained
dynamically from EDID, the default hard-coded HDMI mode is set
to 640x480 @60Hz, which is universally supported.

bug 1495496

Change-Id: I19bc910758015927938fe5dde3e5359a78d905d4
Signed-off-by: Jong Kim <jongk@nvidia.com>
Reviewed-on: http://git-master/r/393564
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Matthew Pedro <mapedro@nvidia.com>
Tested-by: Winnie Hsu <whsu@nvidia.com>