i40e: Annotate struct i40e_qvlist_info with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct i40e_qvlist_info.

Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
Cc: Shiraz Saleem <shiraz.saleem@intel.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
Cc: Gurucharan G <gurucharanx.g@intel.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20231003231838.work.510-kees@kernel.orgSigned-off-by: Kees Cook <keescook@chromium.org>

include/linux/net/intel/i40e_client.h

@@ -45,7 +45,7 @@ struct i40e_qv_info {
 
 struct i40e_qvlist_info {
 	u32 num_vectors;
-	struct i40e_qv_info qv_info[];
+	struct i40e_qv_info qv_info[] __counted_by(num_vectors);
 };