crypto: add missing kernel-doc for anonymous union members

crypto: add missing kernel-doc for anonymous union members

Document the anonymous SKCIPHER_ALG_COMMON and COMP_ALG_COMMON struct
members in skcipher_alg, scomp_alg, and acomp_alg, following the
existing pattern used by HASH_ALG_COMMON in shash_alg.

This fixes the following kernel-doc warnings:

  include/crypto/skcipher.h:166: struct member 'SKCIPHER_ALG_COMMON' not described in 'skcipher_alg'
  include/crypto/internal/scompress.h:39: struct member 'COMP_ALG_COMMON' not described in 'scomp_alg'
  include/crypto/internal/acompress.h:55: struct member 'COMP_ALG_COMMON' not described in 'acomp_alg'

Signed-off-by: Kit Dallege <xaum.io@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>