crypto: api - Move type exit function into crypto_tfm

The type exit function needs to undo any allocations done by the type
init function.  However, the type init function may differ depending
on the upper-level type of the transform (e.g., a crypto_blkcipher
instantiated as a crypto_ablkcipher).

So we need to move the exit function out of the lower-level
structure and into crypto_tfm itself.

As it stands this is a no-op since nobody uses exit functions at
all.  However, all cases where a lower-level type is instantiated
as a different upper-level type (such as blkcipher as ablkcipher)
will be converted such that they allocate the underlying transform
and use that instead of casting (e.g., crypto_ablkcipher casted
into crypto_blkcipher).  That will need to use a different exit
function depending on the upper-level type.

This patch also allows the type init/exit functions to call (or not)
cra_init/cra_exit instead of always calling them from the top level.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/crypto/algapi.h

@@ -23,7 +23,6 @@ struct seq_file;
 struct crypto_type {
 	unsigned int (*ctxsize)(struct crypto_alg *alg, u32 type, u32 mask);
 	int (*init)(struct crypto_tfm *tfm, u32 type, u32 mask);
-	void (*exit)(struct crypto_tfm *tfm);
 	void (*show)(struct seq_file *m, struct crypto_alg *alg);
 };