i965/nir/vec4: Handle uniforms on vertex programs
i965/nir/vec4: Handle uniforms on vertex programs

The implementation takes into account that on ARB_vertex_program
only a single nir variable is generated to support all the uniform data.

Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler