i965/nir: Print NIR on INTEL_DEBUG=fs.
i965/nir: Print NIR on INTEL_DEBUG=fs.

This is useful for debugging and looking for optimization opportunities.

It will need to be expanded when we add support for other scalar stages.

Signed-off-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler