drm/i915: Do not use atomic modesets in hw readout.

This should fix fallout caused by making intel_crtc_control
and update_dpms atomic, which became a problem after reverting the
atomic hw readout patch.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90929


Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>