amd/common: Handle alignment of 96-bit formats.

addrlib doesn't quite do it right, so do it ourselves.

Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2162


CC: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit 88f567b5)