crypto: ccp - Use kmemdup in ccp_copy_and_save_keypart()

Use kmemdup rather than duplicating its implementation

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>