[PATCH] powerpc: implement clear_bit_unlock_is_negative_byte()

[Michael Ellerman]

Nicholas Piggin <npiggin at gmail.com> writes:

> Commit b91e1302ad9b8 ("mm: optimize PageWaiters bit use for
> unlock_page()") added a special bitop function to speed up
> unlock_page(). Implement this for powerpc.

I know you wrote this to work on 32 and 64-bit, but I don't have a good
way to test it on 32-bit at the moment as my 32-bit box is blowing
chunks.

So I've taken this but made it 64-bit only for now.

cheers