hw/nvram/eeprom_at24c: Add init_rom field and at24c_eeprom_init_rom helper

hw/nvram/eeprom_at24c: Add init_rom field and at24c_eeprom_init_rom helper

Allows users to specify binary data to initialize an EEPROM, allowing users to
emulate data programmed at manufacturing time.

- Added init_rom and init_rom_size attributes to TYPE_AT24C_EE
- Added at24c_eeprom_init_rom helper function to initialize attributes
- If -drive property is provided, it overrides init_rom data

Signed-off-by: Peter Delevoryas <peter@pjd.dev>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Corey Minyard <cminyard@mvista.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Ninad Palsule <ninadpalsule@us.ibm.com>
Link: https://lore.kernel.org/r/20230128060543.95582-4-peter@pjd.dev
Signed-off-by: Cédric Le Goater <clg@kaod.org>