crypto: testmgr - add rfc4543(gcm(aes)) decryption test to encryption tests

One "rfc4543(gcm(aes))" decryption test vector doesn't exactly match any of the
encryption test vectors with input and result swapped.  In preparation
for removing the AEAD decryption test vectors and testing AEAD
decryption using the encryption test vectors, add this to the encryption
test vectors, so we don't lose any test coverage.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>