nir: Use a list instead of a hash_table for inputs, outputs, and uniforms

nir: Use a list instead of a hash_table for inputs, outputs, and uniforms

We never did a single hash table lookup in the entire NIR code base that I
found so there was no real benifit to doing it that way.  I suppose that
for linking, we'll probably want to be able to lookup by name but we can
leave building that hash table to the linker.  In the mean time this was
causing problems with GLSL IR -> NIR because GLSL IR doesn't guarantee us
unique names of uniforms, etc.  This was causing massive rendering isues in
the unreal4 Sun Temple demo.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>