st/mesa: fix assertion failures with GL_UNSIGNED_INT64_ARB (v2)

Bindless texture handles can be passed via vertex attribs using this type.
They use the double codepath, so don't use st_pipe_vertex_format.

Cc: 18.0 18.1 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

src/mesa/state_tracker/st_atom_array.c

@@ -324,7 +324,6 @@ static void init_velement_lowered(const struct st_vertex_program *vp,
                                   int src_offset, int instance_divisor,
                                   int vbo_index, int idx)
 {
-   const unsigned format = st_pipe_vertex_format(attrib);
    const GLubyte nr_components = attrib->Size;
 
    if (attrib->Doubles) {
@@ -358,6 +357,8 @@ static void init_velement_lowered(const struct st_vertex_program *vp,
          }
       }
    } else {
+      const unsigned format = st_pipe_vertex_format(attrib);
+
       init_velement(&velements[idx], src_offset,
                     format, instance_divisor, vbo_index);
    }