WAN: Correct comments in hd6457[02].c

Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
diff --git a/drivers/net/wan/hd64570.c b/drivers/net/wan/hd64570.c
index 64ef618..223238d 100644
--- a/drivers/net/wan/hd64570.c
+++ b/drivers/net/wan/hd64570.c
@@ -107,7 +107,7 @@
 
 static inline u16 desc_offset(port_t *port, u16 desc, int transmit)
 {
-	/* Descriptor offset always fits in 16 bytes */
+	/* Descriptor offset always fits in 16 bits */
 	return desc_abs_number(port, desc, transmit) * sizeof(pkt_desc);
 }