anv: Advertise two more formats

anv: Advertise two more formats

These both require swizzling so border colors won't work.  However,
they're conveniently in the list of formats for which custom border
colors require you to specify a format in the sampler.  That list
constists of:

    - VK_FORMAT_B4G4R4A4_UNORM_PACK16
    - VK_FORMAT_B5G6R5_UNORM_PACK16
    - VK_FORMAT_B5G5R5A1_UNORM_PACK16

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6226
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15624>