drm/edid: Populate vrefresh for CEA modes

Well have use for the vrefresh information of CEA modes later. Just
populate the information into the table to avoid having to calculate
it.

I'm too lazy to check if someone relies on newly allocated CEA
modes having 0 vrefresh, so just clear vrefresh back to 0 when
adding the mode to the connector's modelist.

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>