c/main: Remove viewport_id in mesh shader

src/xrt/compositor/main/comp_distortion.c

@@ -552,9 +552,7 @@ comp_distortion_update_uniform_buffer_warp(struct comp_distortion *d,
 	 */
 
 	// clang-format off
-	d->ubo_vp_data[0].viewport_id = 0;
 	d->ubo_vp_data[0].rot = c->xdev->hmd->views[0].rot;
-	d->ubo_vp_data[1].viewport_id = 1;
 	d->ubo_vp_data[1].rot = c->xdev->hmd->views[1].rot;
 
 	memcpy(d->ubo_viewport_handles[0].mapped, &d->ubo_vp_data[0], sizeof(d->ubo_vp_data[0]));

src/xrt/compositor/main/comp_distortion.h

@@ -73,7 +73,6 @@ struct comp_distortion
 	struct
 	{
 		struct xrt_matrix_2x2 rot;
-		int viewport_id;
 		bool flip_y;
 	} ubo_vp_data[2];
 

src/xrt/compositor/shaders/mesh.vert

@@ -8,7 +8,6 @@
 layout (binding = 1, std140) uniform ubo
 {
 	vec4 rot;
-	int viewport_id;
 	bool flip_y;
 } ubo_vp;