dm: Add a simple EEPROM driver

There seem to be a few EEPROM drivers around - perhaps we should have a
single standard one? This simple driver is used for sandbox testing, but
could be pressed into more active service.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

include/dm/uclass-id.h

@@ -32,6 +32,7 @@ enum uclass_id {
 	UCLASS_THERMAL,		/* Thermal sensor */
 	UCLASS_I2C,		/* I2C bus */
 	UCLASS_I2C_GENERIC,	/* Generic I2C device */
+	UCLASS_I2C_EEPROM,	/* I2C EEPROM device */
 
 	UCLASS_COUNT,
 	UCLASS_INVALID = -1,