s390/memory hotplug: use pfmf instruction to initialize storage keys

Move and rename init_storage_keys() to pageattr.c, so it can also be
used from the sclp memory hotplug code in order to initialize
storage keys.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 6d53670..24afd07 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -30,6 +30,8 @@
 #include <asm/setup.h>
 #ifndef __ASSEMBLY__
 
+void storage_key_init_range(unsigned long start, unsigned long end);
+
 static unsigned long pfmf(unsigned long function, unsigned long address)
 {
 	asm volatile(