x86/asm: Ensure asm/proto.h can be included stand-alone

stable inclusion
from stable-5.10.56
commit 02210a5e1894d5da89fbc67f44a182b7739fbaa3
bugzilla: 176004 https://gitee.com/openeuler/kernel/issues/I4DYZ4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=02210a5e1894d5da89fbc67f44a182b7739fbaa3

--------------------------------

[ Upstream commit f7b21a0e ]

Fix:

  ../arch/x86/include/asm/proto.h:14:30: warning: ‘struct task_struct’ declared \
    inside parameter list will not be visible outside of this definition or declaration
  long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2);
                               ^~~~~~~~~~~

  .../arch/x86/include/asm/proto.h:40:34: warning: ‘struct task_struct’ declared \
    inside parameter list will not be visible outside of this definition or declaration
   long do_arch_prctl_common(struct task_struct *task, int option,
                                    ^~~~~~~~~~~

if linux/sched.h hasn't be included previously. This fixes a build error
when this header is used outside of the kernel tree.

 [ bp: Massage commit message. ]
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/b76b4be3-cf66-f6b2-9a6c-3e7ef54f9845@web.deSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/x86/include/asm/proto.h

@@ -4,6 +4,8 @@
 
 #include <asm/ldt.h>
 
+struct task_struct;
+
 /* misc architecture specific prototypes */
 
 void syscall_init(void);