chcr: ensure cntrl is initialized to fix bit-wise or'ing of garabage data

In the case where skb->ip_summed != CHECKSUM_PARTIAL then cntrl contains
garbage value and this is possibly being bit-wise or'd and stored into
cpl->ctrl1.  Fix this by initializing cntrl to zero.

Cleans up clang warning:
drivers/crypto/chelsio/chcr_ipsec.c:374:9: warning: The left expression
of the compound assignment is an uninitialized value. The computed value
will also be garbage

Fixes: 6dad4e8a ("chcr: Add support for Inline IPSec")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>