crypto: doc - fix kernel-doc notation in chacha.c and af_alg.c

Fix function name in chacha.c kernel-doc comment to remove a warning.

Convert af_alg.c to kernel-doc notation to eliminate many kernel-doc
warnings.

../lib/crypto/chacha.c:77: warning: expecting prototype for chacha_block(). Prototype was for chacha_block_generic() instead
chacha.c:104: warning: Excess function parameter 'out' description in 'hchacha_block_generic'

af_alg.c:498: warning: Function parameter or member 'sk' not described in 'af_alg_alloc_tsgl'
../crypto/af_alg.c:539: warning: expecting prototype for aead_count_tsgl(). Prototype was for af_alg_count_tsgl() instead
../crypto/af_alg.c:596: warning: expecting prototype for aead_pull_tsgl(). Prototype was for af_alg_pull_tsgl() instead
af_alg.c:663: warning: Function parameter or member 'areq' not described in 'af_alg_free_areq_sgls'
af_alg.c:700: warning: Function parameter or member 'sk' not described in 'af_alg_wait_for_wmem'
af_alg.c:700: warning: Function parameter or member '...