Moving code around, post classic

[Alyssa Rosenzweig]

>    If we're going to do this, I wonder if we don't want to go even further
>    and get rid of src/gallium/drivers and move the respective folders to
>    src/vendor.** So, instead of src/gallium/drivers/(iris|crocus), we'd have
>    src/intel/gallium/iris and src/intel/gallium/crocus or maybe
>    src/intel/iris and src/intel/crocus.
>    --Jason

If we do that, only one level of indirection -- ie src/intel/(iris|crocus) -- is my preference, because
src/panfrost/gallium/panfrost is a silly path. src/panfrost/gallium or
(ick) src/panfrost/panfrost saves the extra nesting. Same goes for any
vendor with only a single Gallium driver (most of them...?)