crypto: chelsio - remove unused function

Fix the following clang warning:

drivers/crypto/chelsio/chcr_algo.c:129:19: warning: unused function
'is_ofld_imm' [-Wunused-function].

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>