dm: spi: Correct the comment on spi_get_ops()

This comment should refer to SPI, not serial.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>

include/spi.h

@@ -616,7 +616,7 @@ int sandbox_spi_get_emul(struct sandbox_state *state,
 			 struct udevice *bus, struct udevice *slave,
 			 struct udevice **emulp);
 
-/* Access the serial operations for a device */
+/* Access the operations for a SPI device */
 #define spi_get_ops(dev)	((struct dm_spi_ops *)(dev)->driver->ops)
 #define spi_emul_get_ops(dev)	((struct dm_spi_emul_ops *)(dev)->driver->ops)
 #endif /* CONFIG_DM_SPI */