nfp: Use static_assert() to check struct sizes

Commit d88cabfd9abc ("nfp: Avoid -Wflex-array-member-not-at-end warnings") introduced tagged struct nfp_dump_tl_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.

---
 drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c | 2 ++
 1 file changed, 2 insertions(+)

index 2dd37557185e..7276e44a21d0 100644
@@ -41,6 +41,8 @@ struct nfp_dump_tl {
 	);
 	char data[];
 };
+static_assert(offsetof(struct nfp_dump_tl, data) == sizeof(struct nfp_dump_tl_hdr),
+	      "struct member likely outside of struct_group_tagged()");
 
 /* NFP CPP parameters */
 struct nfp_dumpspec_cpp_isl_id {

2.34.1