ksmbd: use aead_request_free to match aead_request_alloc

Use aead_request_free() instead of kfree() to properly free memory
allocated by aead_request_alloc(). This ensures sensitive crypto data
is zeroed before being freed.

Fixes: e2f34481 ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>