i965/nir/vec4: Implement nir_emit_jump
i965/nir/vec4: Implement nir_emit_jump

This implementation is taken as-is from fs_nir.

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

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler