drm/edid: Fix up DMT modes

Liu Lei noticed that our 1856x1392@75Hz DMT mode doesn't match the spec.
Fix that up, and also fix up a few other inconsistencies I discovered
by parsing the spec (DMT version 1.0, revision 13) and comparing the
results to our current DMT mode table.

Also clean up the indentation mess for the 1024x768i mode.

Cc: "liu,lei" <lei.a.liu@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>