b43: rename TMS defines, drop useless condition from core reset

As discussed we do not know band width at core reset time and it is not a good
idea to reset whole just to change band. So just set unconditionally 20 MHz
band width as default during core reset.

As for defines PHY clock changed to band width in specs and it makes much more
sens to call defines by band width which is self-explainable. Updated specs do
not mention 0 value, but comparing to old ones you can notice lineral relation
between PHY clock speed and band width. So it makes sense for 0x0 value to be
10 MHz band width.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>