dt-bindings: remoteproc: stm32-rproc: Add firmware-name property

Add the 'firmware-name' property to the remote processor binding
to allow specifying the default firmware name in the device tree.

Signed-off-by: Arnaud Pouliquen <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mathieu Poirier <[e-mail]>

Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml

···
       If defined, when remoteproc is probed, it loads the default firmware and
       starts the remote processor.
 
+  firmware-name:
+    maxItems: 1
+    description: Default name of the remote processor firmware.
+
 required:
   - compatible
   - reg