how to access TSE control port?

This register is a PHY register, which is accessible through MDIO. To use the TSE's MDIO master, have a look at the datasheet (http://www.altera.com/literature/ug/ug_ethernet.pdf) at pages 6-2 and 6-5. You will need to write first the PHY's MDIO address in mdio_addr0 or mdio_addr1, and then you can directly read/write the PHY's MDIO registers using the MDIO space 0 or 1.

In your example, if you write the PHY's MDIO address in the TSE register mdio_addr1 (0x10) then you can access the extended PHY specific control register through the TSE register 0xB4 (which is 0xA0 "MDIO Space 1" + 20)