IA32 emulation: Fix build problem for modular ia32 a.out support

Commit ce7e5d2d ("x86: fix broken TASK_SIZE for ia32_aout") breaks
kernel builds when "CONFIG_IA32_AOUT=m" with

  ERROR: "set_personality_ia32" [arch/x86/ia32/ia32_aout.ko] undefined!
  make[1]: *** [__modpost] Error 1

The entry point needs to be exported.
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Al Viro <viro@zeniv.linux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/process_64.c

@@ -423,6 +423,7 @@ void set_personality_ia32(bool x32)
 		current_thread_info()->status |= TS_COMPAT;
 	}
 }
+EXPORT_SYMBOL_GPL(set_personality_ia32);
 
 unsigned long get_wchan(struct task_struct *p)
 {