drm/i915/gen9: look for adjusted_mode in the SAGV check for interlaced

We want to look at the mode that we're actually going to set. All the
other display checks for interlaced flags also look at adjusted_mode.

Cc: Lyude <cpaul@redhat.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Lyude <cpaul@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1476131459-23763-2-git-send-email-paulo.r.zanoni@intel.com