drm: radeon: fix error value sign

enable_vblank implementations should use negative result to indicate error.
radeon_enable_vblank() returns EINVAL in this case.  Change this to -EINVAL.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_irq.c b/drivers/gpu/drm/radeon/radeon_irq.c
index 2f349a3..465746b 100644
--- a/drivers/gpu/drm/radeon/radeon_irq.c
+++ b/drivers/gpu/drm/radeon/radeon_irq.c
@@ -76,7 +76,7 @@
 		default:
 			DRM_ERROR("tried to enable vblank on non-existent crtc %d\n",
 				  crtc);
-			return EINVAL;
+			return -EINVAL;
 		}
 	} else {
 		switch (crtc) {
@@ -89,7 +89,7 @@
 		default:
 			DRM_ERROR("tried to enable vblank on non-existent crtc %d\n",
 				  crtc);
-			return EINVAL;
+			return -EINVAL;
 		}
 	}