mailbox: Allow controller specific mapping using fwnode

mailbox: Allow controller specific mapping using fwnode

Introduce optional fw_node() callback which allows a mailbox controller
driver to provide controller specific mapping using fwnode.

The Linux OF framework already implements fwnode operations for the
Linux DD framework so the fw_xlate() callback works fine with device
tree as well.

Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Link: https://lore.kernel.org/r/20250818040920.272664-6-apatel@ventanamicro.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>