spi: tegra210-quad: set half duplex flag

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>