Do not override errors reported by lower layers with generic "-1",
but propagate them to the callers. Change the checks for errors to be
in the form of "if (error)" to maintain consistency.

Link: https://lore.kernel.org/r/20240628224728.2180126-4-dmitry.torokhov@gmail.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>