swr: remove warning about multi-layer surfaces
swr: remove warning about multi-layer surfaces

We now support clearing these, and actually rendering to multiple layers
would require GS support, which will fail in much more spectacular ways
for now. Once that is hooked up, there won't be anything else to do
here.

Signed-off-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>
Reviewed-by: Tim Rowley <54947742fe7299a578dbb84f6c782c6c4c668d8f@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler