dm-crypt: don't initialize cc_sector again

For aead_recheck case, cc_sector has already been initialized in
crypt_convert_init() when trying to re-read the read. Therefore, remove
the duplicated initialization.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>