drm/edid: Fix DMT 1024x768@43Hz (interlaced) timings

One of the VESA DMT timings in drm_dmt_modes[] is slightly off.
1024x768@43Hz (interlaced) vsync_end should be 776, not 772.
This brings it into line with the identical timings in edid_est_modes[].

Signed-off-by: Paul Parsons <lost.distance@yahoo.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160404193639.8631D6E66B@gabe.freedesktop.org