aco/ngg: Use more efficient LDS layout to help reduce bank conflicts.

The LLVM backend has a trick which helps reduce LDS bank conflicts
by swizzling the LDS address where each vertex is emitted.
This commit implements the same thing for ACO.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <mesa/mesa!6964>