b43: LP-PHY: Implement spec updates and remove resolved FIXMEs

Larry has started re-checking all current routines against a new
version of the Broadcom MIPS driver. This patch implements the first
round of changes he documented on the specs wiki.

Also remove a few FIXMEs regarding missing initial values for variables
with dynamic initial values where reading the values has been implemented.

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