rt2x00: Update TX_SW_CFG initvals for 305x SoC

Update TX_SW_CFG initvals for 305x SoC to match with the appropriate
legacy driver.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>