remoteproc: stm32: Improve crash recovery time

When a stop is requested on a crash, it is useless to try to shutdown it
gracefully, it is crashed.

In this case don't send the STM32_MBX_SHUTDOWN mailbox message that
will block the recovery during 500 ms, waiting an answer from the
coprocessor.

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

drivers/remoteproc/stm32_rproc.c

···
 	int err, idx;
 
 	/* request shutdown of the remote processor */
-	if (rproc->state != RPROC_OFFLINE) {
+	if (rproc->state != RPROC_OFFLINE && rproc->state != RPROC_CRASHED) {
 		idx = stm32_rproc_mbox_idx(rproc, STM32_MBX_SHUTDOWN);
 		if (idx >= 0 && ddata->mb[idx].chan) {
 			err = mbox_send_message(ddata->mb[idx].chan, "detach");