Here is a dump from eeprom SAMSUNG UE40C8780XSXZG MainBN94-03469A, BN41-01367A. Mainboard revision is slightly different, but i think they are crosscompatible. You can reflash your 24c256 with content of this archive.
Please dump original eeprom firmware first and keep it in safe place before flashing over new one![:)]( "Smile")
p.s. SoC eeprom is not SPI flash. It is I2C bus eeprom.
p.p.s. Moreover, i think your problem is not related to winbond spi flash, which contains micom firmware. You need to deal with SoC eeprom, which is storage for service menu values you changed to innocent ones.
Please dump original eeprom firmware first and keep it in safe place before flashing over new one
p.s. SoC eeprom is not SPI flash. It is I2C bus eeprom.
p.p.s. Moreover, i think your problem is not related to winbond spi flash, which contains micom firmware. You need to deal with SoC eeprom, which is storage for service menu values you changed to innocent ones.