remoteproc: xlnx: Avoid mailbox setup

remoteproc: xlnx: Avoid mailbox setup

Mailbox properties are optional in the remoteproc xlnx bindings.
If mailbox properties are not found in device-tree it's not fatal error
in the driver. Driver will print warning messages and continue with
normal operation. However, these warning messages can be interpreted as
error. Check "mboxes" and "mbox-names" properties in the driver and setup
mailbox only if they are available in the device-tree.
This will avoid any unwanted warning/error messages.

Signed-off-by: Tanmay Shah <tanmay.shah@amd.com>
Link: https://lore.kernel.org/r/20260303235127.2317955-2-tanmay.shah@amd.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>