dt-bindings: add eeprom "size" property

This adds eeprom "size" as optional property for i2c eeproms.
The "size" property allows explicitly specifying the size of the
EEPROM chip in bytes.

Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Divagar Mohandass <divagar.mohandass@intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>