remoteproc: stm32: Call of_node_put() on iteration error

Function of_phandle_iterator_next() calls of_node_put() on the last
device_node it iterated over, but when the loop exits prematurely it has
to be called explicitly.

Fixes: 13140de0

 ("remoteproc: stm32: add an ST stm32_rproc driver")
Cc: stable@vger.kernel.org
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20230320221826.2728078-2-mathieu.poirier@linaro.org
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>