When eliminating our use of drm_irq_install() I failed to convert
all our synchronize_irq() calls to consult pdev->irq instead of
dev_priv->drm.irq. As we no longer populate dev_priv->drm.irq
we're no longer synchronizing against anything.

v2: Add intel_syncrhonize_irq() (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reported-by: NImre Deak <imre.deak@intel.com>
Fixes: b318b824 ("drm/i915: Nuke drm_driver irq vfuncs")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111012Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190702151723.29739-1-ville.syrjala@linux.intel.com