spi: tegra20-sflash: use to new `spi_transfer_delay_exec`

This conversion to the spi_transfer_delay_exec() helper is not
straightforward, as it seems that when a delay is present, the controller
issues a command, and then a delay is followed.

This change adds support for the new `delay` field which is of type
`spi_delay` and keeps backwards compatibility with the old `delay_usecs`
field.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20190926105147.7839-12-alexandru.ardelean@analog.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-tegra20-sflash.c

@@ -341,10 +341,11 @@ static int tegra_sflash_transfer_one_message(struct spi_master *master,
 			goto exit;
 		}
 		msg->actual_length += xfer->len;
-		if (xfer->cs_change && xfer->delay_usecs) {
+		if (xfer->cs_change &&
+		    (xfer->delay_usecs || xfer->delay.value)) {
 			tegra_sflash_writel(tsd, tsd->def_command_reg,
 					SPI_COMMAND);
-			udelay(xfer->delay_usecs);
+			spi_transfer_delay_exec(xfer);
 		}
 	}
 	ret = 0;