kernel/bpf/verifier: Fix build when NET is not enabled

Fix build errors in kernel/bpf/verifier.c when CONFIG_NET is
not enabled.

../kernel/bpf/verifier.c:3995:13: error: ‘btf_sock_ids’ undeclared here (not in a function); did you mean ‘bpf_sock_ops’?
  .btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],

../kernel/bpf/verifier.c:3995:26: error: ‘BTF_SOCK_TYPE_SOCK_COMMON’ undeclared here (not in a function); did you mean ‘PTR_TO_SOCK_COMMON’?
  .btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],

Fixes: 1df8f55a ("bpf: Enable bpf_skc_to_* sock casting helper to networking prog type")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20201007021613.13646-1-rdunlap@infradead.org

kernel/bpf/verifier.c

@@ -3984,6 +3984,7 @@ static const struct bpf_reg_types sock_types = {
 	},
 };
 
+#ifdef CONFIG_NET
 static const struct bpf_reg_types btf_id_sock_common_types = {
 	.types = {
 		PTR_TO_SOCK_COMMON,
@@ -3994,6 +3995,7 @@ static const struct bpf_reg_types btf_id_sock_common_types = {
 	},
 	.btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
 };
+#endif
 
 static const struct bpf_reg_types mem_types = {
 	.types = {
@@ -4037,7 +4039,9 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_PTR_TO_CTX]		= &context_types,
 	[ARG_PTR_TO_CTX_OR_NULL]	= &context_types,
 	[ARG_PTR_TO_SOCK_COMMON]	= &sock_types,
+#ifdef CONFIG_NET
 	[ARG_PTR_TO_BTF_ID_SOCK_COMMON]	= &btf_id_sock_common_types,
+#endif
 	[ARG_PTR_TO_SOCKET]		= &fullsock_types,
 	[ARG_PTR_TO_SOCKET_OR_NULL]	= &fullsock_types,
 	[ARG_PTR_TO_BTF_ID]		= &btf_ptr_types,