Don't call ath_init() inside the lock.

Yes, this means that sc_invalid is slightly racy, but there are other
issues here which need fixing.

This fixes a source of eventual LORs - ath_init() grabs ATH_LOCK to do
work and releases it before it calls ieee80211_start_all().
ieee80211_start_all() will grab the net80211 comlock to iterate over
the VAPs.

TODO:

* .. I should just migrate the ieee80211_start_all() work to a
  deferred task so it can be done later; it doesn't have to be
  immediately done.

Tested:

* AR5416, STA mode
Shuffle ah_powerMode to be in a sane spot for the given power operation.

This way the state changes from sleep->awake before the registers are poked
and from awake->sleep after the registers are poked.

This way spurious warnings aren't printed by my (to be committed)
debugging code.

Tested:

* AR5416, STA
Add some debugging code to print out if registers are touched whilst the
device is asleep.

This doesn't avoid logging errors for things that are actually OK to
access whilst the chip is asleep (eg, the RTC registers (0x7000->0x70ff
on the AR5416 and later.)

But, this is a pretty good indicator if things are accessed incorrectly.

Tested:

* AR5416, STA