crypto: chelsio - remove set but not used variable 'kctx_len'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/crypto/chelsio/chcr_ipsec.c: In function 'chcr_ipsec_xmit':
drivers/crypto/chelsio/chcr_ipsec.c:674:33: warning:
 variable 'kctx_len' set but not used [-Wunused-but-set-variable]
  unsigned int flits = 0, ndesc, kctx_len;

It not used since commit 8362ea16 ("crypto: chcr - ESN for Inline IPSec Tx")

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