UPSTREAM: nvmem: Add backwards compatibility support for older EEPROM drivers.

UPSTREAM: nvmem: Add backwards compatibility support for older EEPROM drivers.

Older drivers made an 'eeprom' file available in the /sys device
directory. Have the NVMEM core provide this to retain backwards
compatibility.

Change-Id: I03449b029f7595c291144baea4d5fe9969ad7829
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
(cherry pick from b6c217ab9be6895384cf0b284ace84ad79e5c53b)