[bwn] fill out phyctl_1 fields for N-PHY (and later, eventually.)

N-PHY and later require a lot more plcp specific setup for the PHY
to know what to transmit. I've been spoilt by the atheros, intel
and realtek parts where you don't have to hand-assemble the PLCP
but .. well, apparently Broadcom require a lot more work.

This, and PHY-N itself, was the last major missing bit to get 11a
OFDM transmit to work. Without this, CCK transmit worked but
OFDM transmit would always fail (with stat.phy_err set to 0x80.)

I have no idea what 0x80 is, and I went mad reading the broadcom
vendor driver to try and figure it out.

Tested:

• BCM4312 (PHY-LP)
• BCM4321 (PHY-N), 11a, 11bg.