Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/net/r6040.c b/drivers/net/r6040.c
index e3ebd90..200a363 100644
--- a/drivers/net/r6040.c
+++ b/drivers/net/r6040.c
@@ -535,7 +535,7 @@
 			/* RX dribble */
 			if (err & DSC_RX_ERR_DRI)
 				dev->stats.rx_frame_errors++;
-			/* Buffer lenght exceeded */
+			/* Buffer length exceeded */
 			if (err & DSC_RX_ERR_BUF)
 				dev->stats.rx_length_errors++;
 			/* Packet too long */