anv/wsi: Advertise UNORM formats as well as sRGB

anv/wsi: Advertise UNORM formats as well as sRGB

Because WSI images are created with VkImageCreateInfo::flags explicitly set
to 0, they don't ever have the VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT set.
This means that you can't create an image view of it with a different
format so applications can't render directly in sRGB (without automatic
encoding) unless we actually advertise UNORM formats.  There are a lot of
applications that want to do their own sRGB conversion, so we should allow
for that.  We do, however, make UNORM come after sRGB in the list so that
the default for dumb apps that just grab the first thing is to render in
linear and let the sRGB conversion happen automatically.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>