crypto: testmgr - dynamically allocate testvec_config

On arm32, we get warnings about high stack usage in some of the functions:

crypto/testmgr.c:2269:12: error: stack frame size of 1032 bytes in function 'alg_test_aead' [-Werror,-Wframe-larger-than=]
static int alg_test_aead(const struct alg_test_desc *desc, const char *driver,
           ^
crypto/testmgr.c:1693:12: error: stack frame size of 1312 bytes in function '__alg_test_hash' [-Werror,-Wframe-larger-than=]
static int __alg_test_hash(const struct hash_testvec *vecs,
           ^

On of the larger objects on the stack here is struct testvec_config, so
change that to dynamic allocation.

Fixes: 40153b10 ("crypto: testmgr - fuzz AEADs against their generic implementation")
Fixes: d435e10e ("crypto: testmgr - fuzz skciphers against their generic implementation")
Fixes: 9a8a6b3f ("crypto: testmgr - fuzz hashes against their generic implementation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>