mlxsw: i2c: Fix buffer increment counter for write transaction

It fixes a problem for the last chunk where 'chunk_size' is smaller than
MLXSW_I2C_BLK_MAX and data is copied to the wrong offset, overriding
previous data.

Fixes: 6882b0aee180 ("mlxsw: Introduce support for I2C bus")
Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/i2c.c

@@ -294,7 +294,7 @@ mlxsw_i2c_write(struct device *dev, size_t in_mbox_size, u8 *in_mbox, int num,
 		write_tran.len = MLXSW_I2C_ADDR_WIDTH + chunk_size;
 		mlxsw_i2c_set_slave_addr(tran_buf, off);
 		memcpy(&tran_buf[MLXSW_I2C_ADDR_BUF_SIZE], in_mbox +
-		       chunk_size * i, chunk_size);
+		       MLXSW_I2C_BLK_MAX * i, chunk_size);
 
 		j = 0;
 		end = jiffies + timeout;