crypto: qat - Use static_assert() to check struct sizes

Commit 140e4c85 ("crypto: qat - Avoid -Wflex-array-member-not-at-end
warnings") introduced tagged `struct qat_alg_buf_list_hdr`. We want to
ensure that when new members need to be added to the flexible structure,
they are always included within this tagged struct.

So, we use `static_assert()` to ensure that the memory layout for
both the flexible structure and the tagged struct is the same after
any changes.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/intel/qat/qat_common/qat_bl.h

@@ -23,6 +23,8 @@ struct qat_alg_buf_list {
 	);
 	struct qat_alg_buf buffers[];
 } __packed;
+static_assert(offsetof(struct qat_alg_buf_list, buffers) == sizeof(struct qat_alg_buf_list_hdr),
+	      "struct member likely outside of __struct_group()");
 
 struct qat_alg_fixed_buf_list {
 	struct qat_alg_buf_list_hdr sgl_hdr;