mesa/main: Ignore filter state for MS texture completeness

After the discussion in
https://github.com/KhronosGroup/OpenGL-API/issues/45


the section 8.17 (texture completeness) of the OpenGL 4.6 core profile
was changed to explicitly say that multisample texture completeness
ignores filter state of the texture.

"Using the preceding definitions, a texture is complete unless any of the
 following conditions hold true:
   ...
  - The minification filter requires a mipmap (is neither NEAREST nor LINEAR),
    the texture is not multisample, and the texture is not mipmap complete.
  - The texture is not multisample; either the magnification filter is not
    NEAREST, or the minification filter is neither NEAREST nor NEAREST_-
    MIPMAP_NEAREST; and any of
    – The internal format of the texture is integer (see table 8.12).
    – The internal format is STENCIL_INDEX.
    – The internal format is DEPTH_STENCIL, and the value of DEPTH_-
      STENCIL_TEXTURE_MODE for the texture is STENCIL_INDEX."

Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Signed-off-by: Illia Iorin <illia.iorin@globallogic.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit 6b672e34)