cxgb4: Annotate struct clip_tbl 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 checking 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 clip_tbl.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Raju Rangoju <rajur@chelsio.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230929181149.3006432-2-keescook@chromium.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/chelsio/cxgb4/clip_tbl.h

@@ -29,7 +29,7 @@ struct clip_tbl {
 	atomic_t nfree;
 	struct list_head ce_free_head;
 	void *cl_list;
-	struct list_head hash_list[];
+	struct list_head hash_list[] __counted_by(clipt_size);
 };
 
 enum {