uapi: Fix undefined __always_inline on non-glibc systems

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166738

This commit is needed because recent update to include/uapi/linux/ip.h
header broke the build of bpf selftests:

+ pushd tools/testing/selftests
+ /usr/bin/make -s (...)
In file included from In file included from progs/cg_storage_multi_isolated.cprogs/cg_storage_multi_shared.c::9:
9:
/usr/include/linux/ip.h/usr/include/linux/ip.h::103103::22::  error: error: type name requires a specifier or qualifiertype name requires a specifier or qualifier
        __struct_group(/* no tag */, addrs, /* no attrs */,
        ^
        __struct_group(/* no tag */, addrs, /* no attrs */,/usr/include/linux/ip.h
:        ^103
:29: error: expected parameter declarator

The full log can be seen at:
https://kojihub.stream.rdu2.redhat.com/kojifiles/work/tasks/9639/1889639/build.log

The backported commit from upstream here indirectly includes stddef through the
byteorder headers, and this ends up indirectly included through other headers,
fixing the problem. Probably also why upstream doesn't have this problem while
we hit it in centos stream 9.

commit cb8747b
Author: Ismael Luceno <ismael@iodev.co.uk>
Date:   Mon Nov 15 14:46:47 2021 +0100

    uapi: Fix undefined __always_inline on non-glibc systems

    This macro is defined by glibc itself, which makes the issue go unnoticed on
    those systems.  On non-glibc systems it causes build failures on several
    utilities and libraries, like bpftool and objtool.

    Fixes: 1d509f2 ("x86/insn: Support big endian cross-compiles")
    Fixes: 2d7ce0e ("tools/virtio: more stubs")
    Fixes: 3fb321f ("selftests/net: ipv6 flowlabel")
    Fixes: 50b3ed5 ("selftests/bpf: test bpf flow dissection")
    Fixes: 9cacf81 ("bpf: Remove extra lock_sock for TCP_ZEROCOPY_RECEIVE")
    Fixes: a4b2061 ("tools include uapi: Grab a copy of linux/in.h")
    Fixes: b12d6ec ("bpf: btf: add btf print functionality")
    Fixes: c0dd967 ("tools, include: Grab a copy of linux/erspan.h")
    Fixes: c4b6014 ("tools: Add copy of perf_event.h to tools/include/linux/")

    Signed-off-by: Ismael Luceno <ismael@iodev.co.uk>
    Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
    Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
    Link: https://lore.kernel.org/r/20211115134647.1921-1-ismael@iodev.co.uk
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Vasily Gorbik <gor@linux.ibm.com>

Signed-off-by: Herton R. Krzesinski <herton@redhat.com>

Author: Herton R. Krzesinski

include/uapi/linux/byteorder/big_endian.h

@@ -9,6 +9,7 @@
 #define __BIG_ENDIAN_BITFIELD
 #endif
 
+#include <linux/stddef.h>
 #include <linux/types.h>
 #include <linux/swab.h>
 

include/uapi/linux/byteorder/little_endian.h

@@ -9,6 +9,7 @@
 #define __LITTLE_ENDIAN_BITFIELD
 #endif
 
+#include <linux/stddef.h>
 #include <linux/types.h>
 #include <linux/swab.h>