drm/radeon/kms: fix CS alignment checking for tiling (v2)

Covers depth, cb, and textures. Hopefully I got this right.

v2: - fix bugs:
      https://bugs.freedesktop.org/show_bug.cgi?id=28327
      https://bugs.freedesktop.org/show_bug.cgi?id=28381
    - use ALIGNED(), IS_ALIGNED() macros
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>