spi: atmel-quadspi: reject DTR ops

Double Transfer Rate (DTR) ops are added in spi-mem. But this controller
doesn't support DTR transactions. Since we don't use the default
supports_op(), which rejects all DTR ops, do that explicitly in our
supports_op().
Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200623183030.26591-4-p.yadav@ti.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/atmel-quadspi.c

@@ -285,6 +285,12 @@ static bool atmel_qspi_supports_op(struct spi_mem *mem,
 		op->dummy.nbytes == 0)
 		return false;
 
+	/* DTR ops not supported. */
+	if (op->cmd.dtr || op->addr.dtr || op->dummy.dtr || op->data.dtr)
+		return false;
+	if (op->cmd.nbytes != 1)
+		return false;
+
 	return true;
 }