spidev: Add cisco device compatible

Add compatible string for Cisco device present on the Cisco Petra
platform.

Signed-off-by: Daniel Walker <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spidev.c

···
 	{ .compatible = "lwn,bk4" },
 	{ .compatible = "dh,dhcom-board" },
 	{ .compatible = "menlo,m53cpld" },
+	{ .compatible = "cisco,spi-petra" },
 	{},
 };
 MODULE_DEVICE_TABLE(of, spidev_dt_ids);