remoteproc: return error for bad "recovery" debugfs input

If the value written to the "recovery" debugfs file is not one of
the recognized commands return an error to indicate it's invalid.
Signed-off-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20200228183359.16229-5-elder@linaro.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_debugfs.c

@@ -146,6 +146,8 @@ rproc_recovery_write(struct file *filp, const char __user *user_buf,
 	} else if (!strncmp(buf, "recover", count)) {
 		/* begin the recovery process without changing the flag */
 		rproc_trigger_recovery(rproc);
+	} else {
+		return -EINVAL;
 	}
 
 	return count;