bcm43xx-mac80211: Fix machine check on PPC for phy->rev == 1

For BCM4306 chips with phy->rev == 1, several factors in the code lead to machine checks. These are fixed by several kinds of changes. The remaining patches in this series will separate these into correcting typos and problems with the program logic, updates to the specs, and some necessary modifications that are not found in the specs. The latter fixes have previously been required for bcm43xx-softmac, and are clearly noted by comments.