nir/spirv: Allow non-block variables with interface types in lists
nir/spirv: Allow non-block variables with interface types in lists

The original objective was to disallow UBO and SSBO variables from the
variable lists.  This was accidentally broken in b208620fd when fixing some
other interface issues.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler