crypto: ccree - remove set but not used variable 'du_size'

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

drivers/crypto/ccree/cc_cipher.c: In function cc_setup_key_desc:
drivers/crypto/ccree/cc_cipher.c:645:15: warning: variable du_size set but not used [-Wunused-but-set-variable]

It is never used since introduction in
commit dd8486c7 ("crypto: ccree - move key load desc. before flow desc.")

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