anv: set stencil layout for input attachments

anv: set stencil layout for input attachments

If an input attachment has a stencil format, we need to set this.

v2: Fish out VkAttachmentReferenceStencilLayoutKHR from
    VkAttachmentReference2KHR::pNext (Jason)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reported-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Fixes: c1c346f16673 ("anv: implement VK_KHR_separate_depth_stencil_layouts")
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2891>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2891>