eeprom: Zap CONFIG_SYS_EEPROM_X40430

Now that the only user of CONFIG_SYS_EEPROM_X40430 was removed,
remove this unused code from cmd_eeprom.c

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Heiko Schocher <hs@denx.de>
Reviewed-by: Heiko Schocher <hs@denx.de>