drm: bridge: document bridge attach/detach imbalance

Since commit 4a878c03d562 ("drm: bridge: Detach bridge from encoder at
encoder cleanup time"), it is generally no longer correct to detach bridges
from encoders manually. Document that.

Signed-off-by: Peter Rosin <[e-mail]>
Signed-off-by: Andrzej Hajda <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_bridge.c

···
  * If non-NULL the previous bridge must be already attached by a call to this
  * function.
  *
+ * Note that bridges attached to encoders are auto-detached during encoder
+ * cleanup in drm_encoder_cleanup(), so drm_bridge_attach() should generally
+ * *not* be balanced with a drm_bridge_detach() in driver code.
+ *
  * RETURNS:
  * Zero on success, error code on failure
  */