drm/exynos: enable dvi mode for dvi monitor

drm/exynos: enable dvi mode for dvi monitor

Hdmi monitor and dvi monitor can be distinguished with edid.
This patch enables dvi mode if dvi monitor is connected and does
not enable audio feature for dvi mode because dvi has no audio
feature.

This patch is inspired from  commit id:
872d20d66c0b7de0787675dce8569a61e4d9bc0 in drm-next branch.

	BUG=chrome-os-partner:13173
	TEST=Verified that all the dvi related compliance tests pass
		Agilent Technologies,N5998A
		protocol analyser.

Change-Id: I94c7ba951512bb9f1926880e9b8b41d8668495a3
Signed-off-by: Shirish S <s.shirish@samsung.com>
Reviewed-on: https://gerrit.chromium.org/gerrit/31428
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Tested-by: Shirish S <shirish@chromium.org>
Commit-Ready: Shirish S <shirish@chromium.org>