[Accton] Support 0x56 device access via onlp_sfpi_dev_writew/readw

[brandonchuang]

Allow access to Marvell PHY device (0x56) through the following APIs:

onlp_sfpi_dev_readw(int port, uint8_t devaddr, uint8_t addr) onlp_sfpi_dev_writew(int port, uint8_t devaddr, uint8_t addr, uint16_t value) onlp_sfpi_dev_read(int port, uint8_t devaddr, uint8_t addr, uint8_t* rdata, int size) onlp_sfpi_dev_write(int port, uint8_t devaddr, uint8_t addr, uint8_t* data, int size)

Parameter Descriptions: port: Range from 0 to 47, specifies the port number. devaddr: Device address, fixed to 0x56 for the Marvell PHY device. addr: Register address, range from 0 to 0x1F. value: Register value to write, formatted as (High byte << 8) | (Low byte). rdata: Pointer to the buffer where register values will be read into. data: Pointer to the buffer containing the register values to be written. size: Must be greater than 0 and an even value.