dm: usb: Add support for USB keyboards with driver model

Switch USB keyboards over to use driver model instead of scanning with the
horrible usb_get_dev_index() function. This involves creating a new uclass
for keyboards, although so far there is no API.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index 327de34..27fa0b6 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -37,6 +37,7 @@
 	UCLASS_I2C_EEPROM,	/* I2C EEPROM device */
 	UCLASS_I2C_GENERIC,	/* Generic I2C device */
 	UCLASS_I2C_MUX,		/* I2C multiplexer */
+	UCLASS_KEYBOARD,	/* Keyboard input device */
 	UCLASS_LED,		/* Light-emitting diode (LED) */
 	UCLASS_LPC,		/* x86 'low pin count' interface */
 	UCLASS_MASS_STORAGE,	/* Mass storage device */