anv: handle dynamic viewport count

Emit 3DSTATE_CLIP during cmd_buffer_flush_state so that we can change
the max viewport count dynamically.

v2: use one common clip state as size is the same for all gens (Lionel)

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5604>

src/intel/vulkan/anv_private.h

@@ -3385,6 +3385,7 @@ struct anv_graphics_pipeline {
    struct {
       uint32_t                                  sf[7];
       uint32_t                                  depth_stencil_state[3];
+      uint32_t                                  clip[4];
    } gen7;
 
    struct {