staging: kpc2000: kpc2000_spi: Use new structure for SPI transfer delays

In a recent change to the SPI subsystem in commit <bebcfd27>
("spi: introduce `delay` field for `spi_transfer` +
spi_transfer_delay_exec()"), a new `delay` struct was added
to replace the `delay_usecs`. This change replaces the current
`delay_usecs` with `delay` for this driver.

The `spi_transfer_delay_exec()` function [in the SPI framework] makes sure
that both `delay_usecs` & `delay` are used (in this order to preserve
backwards compatibility).
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Link: https://lore.kernel.org/r/20200304073746.19664-1-sergiu.cuciurean@analog.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/kpc2000/kpc2000_spi.c

@@ -386,8 +386,8 @@ kp_spi_transfer_one_message(struct spi_master *master, struct spi_message *m)
 			}
 		}
 
-		if (transfer->delay_usecs)
-			udelay(transfer->delay_usecs);
+		if (transfer->delay.value)
+			ndelay(spi_delay_to_ns(&transfer->delay, transfer));
 	}
 
 	/* de-assert chip select to end the sequence */