cmd: eeprom: add support for layout aware commands

Introduce the (optional) eeprom print and eeprom update commands.

These commands are eeprom layout aware:
* The eeprom print command prints the contents of the eeprom in a human
  readable way (eeprom layout fields, and data formatted to be fit for human
  consumption).
* The eeprom update command allows user to update eeprom fields by specifying
  the field name, and providing the new data in a human readable format (same
  format as displayed by the eeprom print command).
* Both commands can either auto detect the layout, or be told which layout to
  use.

New CONFIG options:
CONFIG_CMD_EEPROM_LAYOUT - enables commands.
CONFIG_EEPROM_LAYOUT_HELP_STRING - tells user what layout names are supported

Feature API:
__weak int parse_layout_version(char *str)
	- override to provide your own layout name parsing
__weak void __eeprom_layout_assign(struct eeprom_layout *layout, int layout_version);
	- override to setup the layout metadata based on the version
__weak int eeprom_layout_detect(unsigned char *data)
	- override to provide your own algorithm for detecting layout version
eeprom_field.c
	- contains various printing and updating functions for common types of
	  eeprom fields. Can be used for defining custom layouts.

Cc: Heiko Schocher <hs@denx.de>
Cc: Marek Vasut <marex@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Cc: Tom Rini <trini@konsulko.com>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>