drm/i915: add helper for checking whether IRQs are enabled

Now that we use the runtime IRQ enable/disable functions in our suspend
path, we can simply check the pm._irqs_disabled flag everywhere.  So
rename it to catch the users, and add an inline for it to make the
checks clear everywhere.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1996,7 +1996,7 @@ static int i915_pc8_status(struct seq_file *m, void *unused)
 
 	seq_printf(m, "GPU idle: %s\n", yesno(!dev_priv->mm.busy));
 	seq_printf(m, "IRQs disabled: %s\n",
-		   yesno(dev_priv->pm.irqs_disabled));
+		   yesno(!intel_irqs_enabled(dev_priv)));
 
 	return 0;
 }