powerpc: Consolidate asm compatibility macros

[Paul Mackerras]

David Gibson writes:

> Hrm.. I actually deliberately removed the L, on the grounds that
> "long" doesn't necessarily have a consistent meaning between C and
> asm.  The idea is that all these operations work on the "natural" size
> for the arch, which is to say the size of the GPRs, which is to say
> the size of a C long.

Yes, long is the type that (happens to) correspond to a register
width, so I like Kumar's suggestion.

Paul.