backend-drm: pass device through atomic commit handler

The atomic commit is device specific. If we have multiple kms devices, we need
to know which device was used for the atomic commit.

Pass the device instead of the backend through the atomic commit.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>

libweston/backend-drm/kms.c

@@ -1184,7 +1184,7 @@ drm_pending_state_apply_atomic(struct drm_pending_state *pending_state,
 		goto out;
 	}
 
-	ret = drmModeAtomicCommit(device->drm.fd, req, flags, b);
+	ret = drmModeAtomicCommit(device->drm.fd, req, flags, device);
 	drm_debug(b, "[atomic] drmModeAtomicCommit\n");
 
 	/* Test commits do not take ownership of the state; return
@@ -1404,8 +1404,8 @@ static void
 atomic_flip_handler(int fd, unsigned int frame, unsigned int sec,
 		    unsigned int usec, unsigned int crtc_id, void *data)
 {
-	struct drm_backend *b = data;
-	struct drm_device *device = b->drm;
+	struct drm_device *device = data;
+	struct drm_backend *b = device->backend;
 	struct drm_crtc *crtc;
 	struct drm_output *output;
 	uint32_t flags = WP_PRESENTATION_FEEDBACK_KIND_VSYNC |