drm/i915: Use the g4x+ approach on gen2 for handling display stuff around GPU reset

drm/i915: Use the g4x+ approach on gen2 for handling display stuff around GPU reset

We don't have GPU reset support for gen2, which means the display
hardware is unaffected when a GPU hang is handled. However as the ring
has in fact stopped, any flips still in the ring will never complete,
and thus the display base address updates will never happen. So we
really need to fix that up manually just like we do on g4x+.

In fact, let's just use intel_has_gpu_reset() instead of IS_GEN2()
since that'll also handle cases where someone would disable the GPU
reset support on gen3/4 for whatever reason.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470428910-12125-5-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>