hwmon: (dell-smm) Return -ENOIOCTLCMD instead of -EINVAL

Returning -ENOIOCTLCMD gives the callers a better
hint of what went wrong and is the recommended
behavior.
Signed-off-by: NArmin Wolf <W_Armin@gmx.de>
Acked-by: NPali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20211021190531.17379-4-W_Armin@gmx.deSigned-off-by: NGuenter Roeck <linux@roeck-us.net>

drivers/hwmon/dell-smm-hwmon.c

@@ -18,6 +18,7 @@
 #include <linux/delay.h>
 #include <linux/dmi.h>
 #include <linux/err.h>
+#include <linux/errno.h>
 #include <linux/hwmon.h>
 #include <linux/init.h>
 #include <linux/module.h>
@@ -516,7 +517,7 @@ i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd
 		break;
 
 	default:
-		return -EINVAL;
+		return -ENOIOCTLCMD;
 	}
 
 	if (val < 0)