nfp: nsp: Annotate struct nfp_eth_table 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 nfp_eth_table.

Cc: Simon Horman <simon.horman@corigine.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Yinjun Zhang <yinjun.zhang@corigine.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Yu Xiao <yu.xiao@corigine.com>
Cc: Sixiang Chen <sixiang.chen@corigine.com>
Cc: oss-drivers@corigine.com
Cc: netdev@vger.kernel.org
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h

@@ -241,7 +241,7 @@ struct nfp_eth_table {
 
 		u64 link_modes_supp[2];
 		u64 link_modes_ad[2];
-	} ports[];
+	} ports[] __counted_by(count);
 };
 
 struct nfp_eth_table *nfp_eth_read_ports(struct nfp_cpp *cpp);