Now that the structures in <crypto/ghash.h> are no longer used, remove
them. Since this leaves <crypto/ghash.h> as just containing constants,
include it from <crypto/gf128hash.h> to deduplicate these definitions.
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260319061723.1140720-19-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>