freedreno/a6xx: un-swap X24S8_UINT

The stencil is actually in the .w component, but we used to use SWAP to
remap the channels.  This doesn't work when tiled/ubwc.

Fixes:
  dEQP-GLES31.functional.stencil_texturing.format.depth24_stencil8_2d_array
  dEQP-GLES31.functional.stencil_texturing.format.depth24_stencil8_cube
  dEQP-GLES31.functional.stencil_texturing.format.stencil_index8_2d_array
  dEQP-GLES31.functional.stencil_texturing.format.stencil_index8_cube
  dEQP-GLES31.functional.stencil_texturing.misc.base_level
  dEQP-GLES31.functional.texture.border_clamp.formats.stencil_index8.nearest_size_pot
  dEQP-GLES31.functional.texture.border_clamp.formats.stencil_index8.nearest_size_npot
  dEQP-GLES31.functional.texture.border_clamp.formats.depth24_stencil8_sample_stencil.nearest_size_pot
  dEQP-GLES31.functional.texture.border_clamp.formats.depth24_stencil8_sample_stencil.nearest_size_npot
  dEQP-GLES31.functional.texture.border_clamp.sampler.uint_stencil

Signed-off-by: Rob Clark <robdclark@chromium.org>
(cherry picked from commit 4e72abcd)