b43: Fix and update LP-PHY code

-Fix a few nasty typos (b43_phy_* operations instead of b43_radio_*)
 in the channel tune routines.
-Fix some typos & spec errors found by MMIO tracing.
-Optimize b43_phy_write & b43_phy_mask/set/maskset to use
 only the minimal number of MMIO accesses. (Write is possible
 using a single 32-bit MMIO write, while set/mask/maskset can
 be done in 3 16-bit MMIOs).
-Set the default channel back to 1, as the bug forcing us to use
 channel 7 is now fixed.

With this, the device comes up, scans, associates, transmits,
receives, monitors and injects on all channels - in other words,
it's fully functional. Sensitivity and TX power are still sub-optimal,
due to the lack of calibration (that's next on my list).

Signed-off-by: Gábor Stefanik <netrolller.3d@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>