x86/32: Remove unused IA32_STACK_TOP and two externs

Since

  32974ad ("[IA64] Remove COMPAT_IA32 support")

IA32_STACK_TOP and ia32_setup_arg_pages() are not used anymore.

And

  675a081 ("x86: unify mmap_{32|64}.c")

left behind ia32_pick_mmap_layout() extern declaration.

Remove them all.

  [ bp: Massage commit message. ]

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230625125411.25840-1-yuehaibing@huawei.com

Author: YueHaibing

arch/x86/include/asm/ia32.h

@@ -56,17 +56,6 @@ struct stat64 {
 	unsigned long long	st_ino;
 } __attribute__((packed));
 
-#define IA32_STACK_TOP IA32_PAGE_OFFSET
-
-#ifdef __KERNEL__
-struct linux_binprm;
-extern int ia32_setup_arg_pages(struct linux_binprm *bprm,
-				unsigned long stack_top, int exec_stack);
-struct mm_struct;
-extern void ia32_pick_mmap_layout(struct mm_struct *mm);
-
-#endif
-
 extern bool __ia32_enabled;
 
 static __always_inline bool ia32_enabled(void)