panvk/csf: explicitly set ls_sb_slot in set_fbds_provoking_vertex

SB_ID(LS) is currently equal to zero, so this is not a behavior change,
but worth setting it explicitly for clarity and in case the sb
assignments change.

Signed-off-by: Olivia Lee <olivia.lee@collabora.com>
Fixes: 885805560f ("panvk/csf: fix case where vk_meta is used before PROVOKING_VERTEX_MODE_LAST")
Reviewed-by: Eric R. Smith <eric.smith@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38458>

src/panfrost/vulkan/csf/panvk_vX_cmd_draw.c

@@ -71,6 +71,7 @@ generate_fn_set_fbds_provoking_vertex(struct panvk_device *dev,
       .nr_registers = csif_info->cs_reg_count,
       .nr_kernel_registers = MAX2(csif_info->unpreserved_cs_reg_count, 4),
       .reg_perm = provoking_vertex_fn_reg_perm_cb,
+      .ls_sb_slot = SB_ID(LS),
    };
    cs_builder_init(&b, &conf, fn_mem);