drivers: i2c: Correct i2c_dw target implementation

The I2C target implementation for i2c_dw does not follow the
zephyr target specification. The following three issues are corrected:

1) The read_requested CB is called on every byte of the transaction
    - it must be called only on the first byte of the transaction
2) The read_processed CB is called on every byte of the transaction
    - it must be called only on bytes following the first byte
3) Bytes returned in the data ptr param of read_processed are not
    sent to the controller
     -These bytes must be sent to the controller

Signed-off-by: James Growden <jgrowden@tenstorrent.com>