spi/atmel: typo in debug message

This patches a typo in the debug message.
Signed-off-by: NMatthias Brugger <mensch0815@gmail.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

drivers/spi/atmel_spi.c

@@ -679,7 +679,7 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
 			bits = (asd->csr >> 4) & 0xf;
 			if (bits != xfer->bits_per_word - 8) {
 				dev_dbg(&spi->dev, "you can't yet change "
-					 "bit_per_word in transfers\n");
+					 "bits_per_word in transfers\n");
 				return -ENOPROTOOPT;
 			}
 		}