Convert CONFIG_CMD_EEPROM et al to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_EEPROM
   CONFIG_CMD_EEPROM_LAYOUT
   CONFIG_EEPROM_LAYOUT_HELP_STRING

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
[trini: Rework Kconfig logic slightly, define EEPROM location on TI eval
platforms]
Signed-off-by: Tom Rini <trini@konsulko.com>