remoteproc: Properly deal with a detach request when attached

This patch introduces the capability to detach a remote processor
that has been attached to by the remoteproc core. For that to happen
a rproc::ops::detach() operation needs to be available.

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

drivers/remoteproc/remoteproc_cdev.c

···
 			return -EINVAL;
 
 		rproc_shutdown(rproc);
+	} else if (!strncmp(cmd, "detach", len)) {
+		if (rproc->state != RPROC_ATTACHED)
+			return -EINVAL;
+
+		ret = rproc_detach(rproc);
 	} else {
 		dev_err(&rproc->dev, "Unrecognized option\n");
 		ret = -EINVAL;

drivers/remoteproc/remoteproc_sysfs.c

···
 			return -EINVAL;
 
 		rproc_shutdown(rproc);
+	} else if (sysfs_streq(buf, "detach")) {
+		if (rproc->state != RPROC_ATTACHED)
+			return -EINVAL;
+
+		ret = rproc_detach(rproc);
 	} else {
 		dev_err(&rproc->dev, "Unrecognised option: %s\n", buf);
 		ret = -EINVAL;