crypto/dpaa_sec: improve memory freeing

crypto/dpaa_sec: improve memory freeing

This patch fixes management of memory for authentication
and encryption keys.
There were two issues with former state of implementation:

1) Invalid access to dpaa_sec_session union members
    The dpaa_sec_session structure includes an anonymous union:
    union {
        struct {...} aead_key;
        struct {
            struct {...} cipher_key;
            struct {...} auth_key;
        };
    };
    Depending on the used algorithm a rte_zmalloc() function
    allocated memory that was kept in aead_key, cipher_key
    or auth_key. However every time the memory was released,
    rte_free() was called only on cipher and auth keys, even
    if pointer to allocated memory was stored in aead_key.

    The C language specification defines such behavior as undefined.
    As the cipher_key and aead_key are similar, have same sizes and
    alignment, it has worked, but it's directly against C specification.

    This patch fixes this, providing a free_session_data() function
    to free the keys data. It verifies which algorithm was used
    (aead or auth+cipher) and frees proper part of the union.

2) Some keys might have been freed multiple times
    In functions like: dpaa_sec_cipher_init(), dpaa_sec_auth_init(),
    dpaa_sec_chain_init(), dpaa_sec_aead_init() keys data were freed
    before returning due to some error conditions. However the pointers
    were not zeroed causing another calls to ret_free from higher
    layers of code. This causes an error log about invalid memory address
    to be printed.

    This patch fixes it by making only one layer responsible for freeing
    memory

Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
Acked-by: Akhil Goyal <akhil.goyal@nxp.com>