[CRYPTO] crc32c: Fix unconventional setkey usage

The convention for setkey is that once it is set it should not change,
in particular, init must not wipe out the key set by it.  In fact, init
should always be used after setkey before any digestion is performed.

The only user of crc32c that sets the key is tcrypt.  This patch adds
the necessary init calls there.

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