meta: Use ARB_explicit_attrib_location in the rest of the meta shaders.

meta: Use ARB_explicit_attrib_location in the rest of the meta shaders.

This is cleaner than using glBindAttribLocation().

Not all drivers support the extension, but I don't think those drivers
use GLSL in the first place.  Apparently some Meta shaders already use
GL_ARB_explicit_attrib_location, so I think it should be okay.

Honestly, I'm not sure how the old code worked anyway - we bound the
attribute location for "texcoords", while all the shaders capitalized
or spelled it differently.

v2: Convert another instance in brw_meta_fast_clear.c.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>