perf tests x86: Move insn.h include to make sure it finds stddef.h

In some versions of alpine Linux the perf build is broken since commit
1d509f2a ("x86/insn: Support big endian cross-compiles"):

  In file included from /usr/include/linux/byteorder/little_endian.h:13,
                   from /usr/include/asm/byteorder.h:5,
                   from arch/x86/util/../../../../arch/x86/include/asm/insn.h:10,
                   from arch/x86/util/archinsn.c:2:
  /usr/include/linux/swab.h:161:8: error: unknown type name '__always_inline'
   static __always_inline __u16 __swab16p(const __u16 *p)

So move the inclusion of arch/x86/include/asm/insn.h to later in the
places where linux/stddef.h (that conditionally defines
__always_inline) to workaround this problem on Alpine Linux 3.9 to 3.11,
3.12 onwards works.

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/x86/tests/insn-x86.c

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/types.h>
-#include "../../../../arch/x86/include/asm/insn.h"
 #include <string.h>
 
 #include "debug.h"
 #include "tests/tests.h"
 #include "arch-tests.h"
+#include "../../../../arch/x86/include/asm/insn.h"
 
 #include "intel-pt-decoder/intel-pt-insn-decoder.h"
 

tools/perf/arch/x86/util/archinsn.c

 // SPDX-License-Identifier: GPL-2.0
-#include "../../../../arch/x86/include/asm/insn.h"
 #include "archinsn.h"
 #include "event.h"
 #include "machine.h"
 #include "thread.h"
 #include "symbol.h"
+#include "../../../../arch/x86/include/asm/insn.h"
 
 void arch_fetch_insn(struct perf_sample *sample,
 		     struct thread *thread,