llvmpipe: add array/3d clearing support

Fixes:
dEQP-VK.pipeline.multisample.sampled_image.64x64_4.*.samples_4

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6381>
diff --git a/src/gallium/drivers/llvmpipe/lp_surface.c b/src/gallium/drivers/llvmpipe/lp_surface.c
index 2a60d86..af8ada4 100644
--- a/src/gallium/drivers/llvmpipe/lp_surface.c
+++ b/src/gallium/drivers/llvmpipe/lp_surface.c
@@ -313,6 +313,10 @@
    if (dst->texture->nr_samples > 1) {
       struct pipe_box box;
       u_box_2d(dstx, dsty, width, height, &box);
+      if (dst->texture->target != PIPE_BUFFER) {
+         box.z = dst->u.tex.first_layer;
+         box.depth = dst->u.tex.last_layer - dst->u.tex.first_layer + 1;
+      }
       for (unsigned s = 0; s < util_res_sample_count(dst->texture); s++) {
          lp_clear_color_texture_msaa(pipe, dst->texture, dst->format,
                                      color, s, &box);
@@ -378,6 +382,10 @@
       uint64_t zstencil = util_pack64_z_stencil(dst->format, depth, stencil);
       struct pipe_box box;
       u_box_2d(dstx, dsty, width, height, &box);
+      if (dst->texture->target != PIPE_BUFFER) {
+         box.z = dst->u.tex.first_layer;
+         box.depth = dst->u.tex.last_layer - dst->u.tex.first_layer + 1;
+      }
       for (unsigned s = 0; s < util_res_sample_count(dst->texture); s++)
          lp_clear_depth_stencil_texture_msaa(pipe, dst->texture,
                                              dst->format, clear_flags,