The ghash and poly1305 hash implementations can be enabled when
CONFIG_CRYPTO_HASH is turned off, causing a link error:

crypto/built-in.o: In function `ghash_mod_init':
(.init.text+0xd0): undefined reference to `crypto_register_shash'
crypto/built-in.o: In function `ghash_mod_exit':
(.exit.text+0xb4): undefined reference to `crypto_unregister_shash'
crypto/built-in.o: In function `poly1305_mod_init':
(.init.text+0xb4): undefined reference to `crypto_register_shash'
crypto/built-in.o: In function `poly1305_mod_exit':
(.exit.text+0x98): undefined reference to `crypto_unregister_shash'

This adds an explicit 'select', like all other hashes have it.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>