x86: process_64.c declare __switch_to() and sys_arch_prctl before they get used

Impact: cleanup

In asm/system.h moved out __switch_to from CONFIG_X86_32 as it is common for
both 32 and 64 bit.

In asm/pctl.h defined sys_arch_prctl
Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/prctl.h

@@ -6,5 +6,8 @@
 #define ARCH_GET_FS 0x1003
 #define ARCH_GET_GS 0x1004
 
+#ifdef CONFIG_X86_64
+extern long sys_arch_prctl(int, unsigned long);
+#endif /* CONFIG_X86_64 */
 
 #endif /* _ASM_X86_PRCTL_H */

arch/x86/include/asm/system.h

@@ -17,12 +17,12 @@
 # define AT_VECTOR_SIZE_ARCH 1
 #endif
 
-#ifdef CONFIG_X86_32
-
 struct task_struct; /* one of the stranger aspects of C forward declarations */
 struct task_struct *__switch_to(struct task_struct *prev,
 				struct task_struct *next);
 
+#ifdef CONFIG_X86_32
+
 /*
  * Saving eflags is important. It switches not only IOPL between tasks,
  * it also protects other tasks from NT leaking through sysenter etc.