[S390] pm: add kernel_page_present

Fix the following build failure caused by make allyesconfig using
CONFIG_HIBERNATION and CONFIG_DEBUG_PAGEALLOC

kernel/built-in.o: In function `saveable_page':
kernel/power/snapshot.c:897: undefined reference to `kernel_page_present'
kernel/built-in.o: In function `safe_copy_page':
kernel/power/snapshot.c:948: undefined reference to `kernel_page_present'
make: *** [.tmp_vmlinux1] Error 1

Signed-off-by: Hans-Joachim Picht <hans@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/mm/pgtable.c

@@ -313,3 +313,22 @@ int s390_enable_sie(void)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(s390_enable_sie);
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
+#ifdef CONFIG_HIBERNATION
+bool kernel_page_present(struct page *page)
+{
+	unsigned long addr;
+	int cc;
+
+	addr = page_to_phys(page);
+	asm("lra %1,0(%1)\n"
+	    "ipm %0\n"
+	    "srl %0,28"
+	    :"=d"(cc),"+a"(addr)::"cc");
+	return cc == 0;
+}
+
+#endif /* CONFIG_HIBERNATION */
+#endif /* CONFIG_DEBUG_PAGEALLOC */
+