cipher: Slight refactoring of kem.c.
* cipher/kem.c (_gcry_kem_keypair): Do not claim used variables. Slight refactoring to allow for a enum-case check. (_gcry_kem_encap): Ditto. (_gcry_kem_decap): Ditto. * cipher/kyber.h (crypto_kem_keypair_3) [KYBER_K]: Fix syntax error.