dm: spi: Change cs_info op to return -EINVAL for invalid cs num

We need distinguish the following two situations in various SPI APIs:

- given chip select num is invalid
- given chip select num is valid, but no device is attached

Currently -ENODEV is returned for both cases.

For the first case, it's more reasonable to return -EINVAL instead of
-ENODEV for invalid chip select numbers.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com> # SoPine
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>

drivers/spi/tegra20_sflash.c

@@ -78,7 +78,7 @@ int tegra20_sflash_cs_info(struct udevice *bus, unsigned int cs,
 {
 	/* Tegra20 SPI-Flash - only 1 device ('bus/cs') */
 	if (cs != 0)
-		return -ENODEV;
+		return -EINVAL;
 	else
 		return 0;
 }