ACPI: sysfs: Clean up create_pnp_modalias() and create_of_modalias()

'modalias' is only written with snprintf() and it is already guaranteed
to be nul-terminated, so remove the unneeded (but harmless) writes of a
trailing '\0' to it.

Also snprintf() never returns negative values, so remove redundant (but
harmless) checks for it.

Signed-off-by: Christophe JAILLET <[e-mail]>
[ rjw: Merge two patches into one, combine changelogs, add subject ]
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/device_sysfs.c

···
 			continue;
 
 		count = snprintf(&modalias[len], size, "%s:", id->id);
-		if (count < 0)
-			return -EINVAL;
 
 		if (count >= size)
 			return -ENOMEM;
···
 		len += count;
 		size -= count;
 	}
-	modalias[len] = '\0';
+
 	return len;
 }
 
···
 	for (i = 0; i < nval; i++, obj++) {
 		count = snprintf(&modalias[len], size, "C%s",
 				 obj->string.pointer);
-		if (count < 0)
-			return -EINVAL;
 
 		if (count >= size)
 			return -ENOMEM;
···
 		len += count;
 		size -= count;
 	}
-	modalias[len] = '\0';
+
 	return len;
 }