[PATCH 2/3] drm/panfrost: Use u64 for size in lock_region

[Alyssa Rosenzweig]

> > Mali virtual addresses are 48-bit. Use a u64 instead of size_t to ensure
> > we can express the "lock everything" condition as ~0ULL without relying
> > on platform-specific behaviour.
> 
> 'platform-specific behaviour' makes it sound like this is something to
> do with a particular board. This is 32bit/64bit - it's going to be
> broken on 32bit: large lock regions are not going to work.

Oh, my. I used the term as a weasel word since the spec is loose on how
big a size_t actually is. But if this is causing actual breakage on
armv7 we're in trouble. I'll add a Cc stable tag on v2, unless the Fixes
implies that?

Thanks for pointing this out.