ARM: mvebu: update EEPROM description of Armada 388 GP

Contrary to what the Device Tree indicates, the EEPROM at 0x54 is not
populated, so we get rid of this comment.

However, there is an EEPROM at 0x57, so we add support for this
AT24C64 EEPROM:

$ hexdump -C /sys/bus/i2c/devices/0-0057/eeprom
00000000  0c ff f3 ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
00000010  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
*
00002000

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>