spi: tegra210-quad: set half duplex flag

BugLink: https://bugs.launchpad.net/bugs/2024857

Tegra QSPI controller only supports half duplex transfers.
Set half duplex constrain flag.

Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
Link: https://lore.kernel.org/r/20230223162635.19747-3-kyarlagadda@nvidia.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
(cherry picked from commit f7482d8)
Acked-by: Jamie Nguyen <jamien@nvidia.com>
Acked-by: Brad Figg <bfigg@nvidia.com>
Acked-by: Ian May <ian.may@canonical.com>
Acked-by: Jacob Martin <jacob.martin@canonical.com>
Signed-off-by: Brad Figg <bfigg@nvidia.com>

Author: kkyarlagadda

drivers/spi/spi-tegra210-quad.c

@@ -1550,6 +1550,7 @@ static int tegra_qspi_probe(struct platform_device *pdev)
 	master->mode_bits = SPI_MODE_0 | SPI_MODE_3 | SPI_CS_HIGH |
 			    SPI_TX_DUAL | SPI_RX_DUAL | SPI_TX_QUAD | SPI_RX_QUAD;
 	master->bits_per_word_mask = SPI_BPW_MASK(32) | SPI_BPW_MASK(16) | SPI_BPW_MASK(8);
+	master->flags = SPI_CONTROLLER_HALF_DUPLEX;
 	master->setup = tegra_qspi_setup;
 	master->transfer_one_message = tegra_qspi_transfer_one_message;
 	master->num_chipselect = 1;