[PATCH bpf-next] selftests/bpf: Fix a selftest compilation error

[Yonghong Song <yonghong.song@linux.dev>]

When building the kernel and selftest with clang compiler (llvm17 or llvm18),
I hit the following compilation failure:
  In file included from progs/test_lwt_redirect.c:3:
  In file included from /usr/include/linux/ip.h:21:
  In file included from /usr/include/asm/byteorder.h:5:
  In file included from /usr/include/linux/byteorder/little_endian.h:13:
  /usr/include/linux/swab.h:136:8: error: unknown type name '__always_inline'
    136 | static __always_inline unsigned long __swab(const unsigned long y)
        |        ^
  /usr/include/linux/swab.h:171:8: error: unknown type name '__always_inline'
    171 | static __always_inline __u16 __swab16p(const __u16 *p)
  ...

bpf_helpers.h file provided a definition for __always_inline.
Putting 'ip.h' after 'bpf_helpers.h' fixed the issue.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
 tools/testing/selftests/bpf/progs/test_lwt_redirect.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/progs/test_lwt_redirect.c b/tools/testing/selftests/bpf/progs/test_lwt_redirect.c
index 7ab1fd310efb..8c895122f293 100644
--- a/tools/testing/selftests/bpf/progs/test_lwt_redirect.c
+++ b/tools/testing/selftests/bpf/progs/test_lwt_redirect.c
@@ -1,8 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/bpf.h>
-#include <linux/ip.h>
 #include <bpf/bpf_endian.h>
 #include <bpf/bpf_helpers.h>
+#include <linux/ip.h>
 #include "bpf_tracing_net.h"
 
 /* We don't care about whether the packet can be received by network stack.
-- 
2.34.1