drm/radeon: Restore sw interrupt on resume

Fixes performance drop after suspend/resume on some systems.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/char/drm/radeon_irq.c b/drivers/char/drm/radeon_irq.c
index 009af38..ee40d19 100644
--- a/drivers/char/drm/radeon_irq.c
+++ b/drivers/char/drm/radeon_irq.c
@@ -234,7 +234,7 @@
 	return radeon_wait_irq(dev, irqwait->irq_seq);
 }
 
-static void radeon_enable_interrupt(struct drm_device *dev)
+void radeon_enable_interrupt(struct drm_device *dev)
 {
 	drm_radeon_private_t *dev_priv = (drm_radeon_private_t *) dev->dev_private;