[PATCH 2/3] pm: Handle HID0_SLEEP in the TLF_NAPPING hack.

[Paul Mackerras]

Scott Wood writes:

> The e300 core (and probably most other 6xx chips) can only come out of
> sleep mode with an interrupt.  However, interrupts are logically disabled
> by the power management layer.
> 
> This hack extends the existing doze/nap hack to also suppress the running
> of the interrupt handler when in sleep mode.

Having thought about this for a bit, I have come to the conclusion
that it would be a lot cleaner to use a new TLF_SLEEPING bit rather
than having to read HID0 to know whether we were napping or sleeping.
There are plenty of bits left in thread_info.local_flags; we've only
used 1 so far. :)

Paul.