Add some debugging code to print out if registers are touched whilst the

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