spi: cadence-quadspi: Provide a capability structure

This controller has DTR support, so advertize it with a capability now
that the spi-controller structure contains this new field. This will
later be used by the core to discriminate whether an operation is
supported or not, in a more generic way than having different helpers.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/linux-mtd/20220127091808.1043392-4-miquel.raynal@bootlin.com

drivers/spi/spi-cadence-quadspi.c

@@ -1595,6 +1595,10 @@ static const struct spi_controller_mem_ops cqspi_mem_ops = {
 	.supports_op = cqspi_supports_mem_op,
 };
 
+static const struct spi_controller_mem_caps cqspi_mem_caps = {
+	.dtr = true,
+};
+
 static int cqspi_setup_flash(struct cqspi_st *cqspi)
 {
 	struct platform_device *pdev = cqspi->pdev;
@@ -1652,6 +1656,7 @@ static int cqspi_probe(struct platform_device *pdev)
 	}
 	master->mode_bits = SPI_RX_QUAD | SPI_RX_DUAL;
 	master->mem_ops = &cqspi_mem_ops;
+	master->mem_caps = &cqspi_mem_caps;
 	master->dev.of_node = pdev->dev.of_node;
 
 	cqspi = spi_master_get_devdata(master);