b43: HT-PHY: do some extra TSSI setup after configuring TX

After b43_phy_ht_tx_power_ctl_setup there are some extra radio ops:
 radio_read(0x08bf) -> 0x0001
radio_write(0x08bf) <- 0x0001
radio_write(0x0159) <- 0x0011
On N-PHY we write 0x11 to TSSI regs, so it's probably sth similar.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>