drm/atomic: Save flip flags in drm_crtc_state

Allows using atomic flip helpers for drivers
using ASYNC flip.
Remove ASYNC_FLIP restriction in helpers and
caches the page flip flags in drm_crtc_state
to be used in the low level drivers.

v2:
Resending the patch since the original was broken.

v3:
Save flag in crtc_state instead of plane_state

v4:
Reset the flag before using again.

v5:
Fix type in header.
Rename the field to pageflip_flags.
Remove unrelated hunk.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1486072591-3893-2-git-send-email-Andrey.Grodzovsky@amd.com
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 8f0b195..c38a572 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -155,10 +155,17 @@ struct drm_crtc_state {
 	 * Target vertical blank period when a page flip
 	 * should take effect.
 	 */
-
 	u32 target_vblank;
 
 	/**
+	 * @pageflip_flags:
+	 *
+	 * DRM_MODE_PAGE_FLIP_* flags, as passed to the page flip ioctl.
+	 * Zero in any other case.
+	 */
+	u32 pageflip_flags;
+
+	/**
 	 * @event:
 	 *
 	 * Optional pointer to a DRM event to signal upon completion of the