b43: LP-PHY: Update code for spec fixes, and fix a few typos

A few typos have been discovered in both the specs and the code.
This patch fixes them.

Also use lpphy_op_switch_channel consistently, and make all users
of it print its return value for easier debugging.

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