x86/pti: Make pti_set_kernel_image_nonglobal() static

pti_set_kernel_image_nonglobal() is only used in pti.c, make it static.
Signed-off-by: NJiang Biao <jiang.biao2@zte.com.cn>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NDave Hansen <dave.hansen@linux.intel.com>
Cc: luto@kernel.org
Cc: hpa@zytor.com
Cc: albcamus@gmail.com
Cc: zhong.weidong@zte.com.cn
Link: https://lkml.kernel.org/r/1531713820-24544-4-git-send-email-jiang.biao2@zte.com.cn

arch/x86/mm/pti.c

@@ -466,7 +466,7 @@ void pti_clone_kernel_text(void)
  * the other set_memory.h functions.  Just extern it.
  */
 extern int set_memory_nonglobal(unsigned long addr, int numpages);
-void pti_set_kernel_image_nonglobal(void)
+static void pti_set_kernel_image_nonglobal(void)
 {
 	/*
 	 * The identity map is created with PMDs, regardless of the