drm/i915: Move check_digital_port_conflicts() earier

drm/i915: Move check_digital_port_conflicts() earier

check_digital_port_conflicts() is done needlessly late. Move it earlier.
This will be needed as later on we want to set any_ms=true a bit later
for non-modesets too and we can't call this guy without the
connection_mutex held.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191015193035.25982-4-ville.syrjala@linux.intel.com
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>