mesa/teximage: Fix S3TC regression due to ASTC interaction

mesa/teximage: Fix S3TC regression due to ASTC interaction

A prior, literal reading of the ASTC spec led to the prohibition
of some compressed formats being used against the targets:
TEXTURE_CUBE_MAP_ARRAY and TEXTURE_3D. Since the spec does not specify
interactions with other extensions for specific compressed textures,
remove such interactions.

Fixes the following Piglit tests on Gen9:
piglit.spec.arb_direct_state_access.getcompressedtextureimage
piglit.spec.arb_get_texture_sub_image.arb_get_texture_sub_image-getcompressed
piglit.spec.arb_texture_cube_map_array.fbo-generatemipmap-cubemap array s3tc_dxt1
piglit.spec.ext_texture_compression_s3tc.getteximage-targets cube_array s3tc

v2. Don't interact with other specific compressed formats (Ian).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91927
Suggested-by: Neil Roberts <neil@linux.intel.com>
Signed-off-by: Nanley Chery <nanley.g.chery@intel.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>