glsl: Don't require matching centroid qualifiers

glsl: Don't require matching centroid qualifiers

Note: This patch appears to violate older OpenGL and OpenGLES specs.

The OpenGLES GLSL 3.1 and OpenGL GLSL 4.3 specifications both remove
the requirement for the output and input centroid qualifiers to match.

The deqp
dEQP-GLES3.functional.shaders.linkage.varying.rules.differing_interpolation_2
test wants the newer OpenGLES 3.1 specification behavior, even for
OpenGLES 3.0. This patch simply removes the checking in all cases.

The OpenGLES 3.0 conformance test suite doesn't appear to require the
older ("must match") spec behavior.

For reference, here are the relavent spec citations:

  The OpenGL 4.2 spec says: "the last active shader stage output
  variables and fragment shader input variables of the same name must
  match in type and qualification (other than out matching to in)"

  The OpenGL 4.3 spec says: "interpolation qualification (e.g., flat)
  and auxiliary qualification (e.g. centroid) may differ."

  The OpenGLES GLSL 3.00.4 specification says: "The output of the
  vertex shader and the input of the fragment shader form an
  interface. For this interface, vertex shader output variables and
  fragment shader input variables of the same name must match in type
  and qualification (other than precision and out matching to in)."

  The OpenGLES GLSL 3.10 Specification says: "interpolation
  qualification (e.g., flat) and auxiliary qualification (e.g.
  centroid) may differ"

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92743
Bugzilla: https://cvs.khronos.org/bugzilla/show_bug.cgi?id=7819
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>