remoteproc: stm32_rproc: Allow to specify firmware default name

Enhance the stm32_rproc driver to allow enabling the configuration of the
firmware name based on the 'firmware-name' property in the device tree,
offering flexibility compared to using the remote proc device node
name.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20250327082721.641278-3-arnaud.pouliquen@foss.st.com


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>