[S390] sclp: avoid 64 bit division

Avoid 64 bit division to fix this compile error on 32 bit:
drivers/s390/char/sclp_cmd.c:711: undefined reference to `__udivdi3'

Also move the whole arch_get_memory_phys_device function to the
memory hotplug related functions.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/sclp_cmd.c

@@ -308,6 +308,13 @@ struct assign_storage_sccb {
 	u16 rn;
 } __packed;
 
+int arch_get_memory_phys_device(unsigned long start_pfn)
+{
+	if (!rzm)
+		return 0;
+	return PFN_PHYS(start_pfn) >> ilog2(rzm);
+}
+
 static unsigned long long rn2addr(u16 rn)
 {
 	return (unsigned long long) (rn - 1) * rzm;
@@ -704,13 +711,6 @@ int sclp_chp_deconfigure(struct chp_id chpid)
 	return do_chp_configure(SCLP_CMDW_DECONFIGURE_CHPATH | chpid.id << 8);
 }
 
-int arch_get_memory_phys_device(unsigned long start_pfn)
-{
-	if (!rzm)
-		return 0;
-	return PFN_PHYS(start_pfn) / rzm;
-}
-
 struct chp_info_sccb {
 	struct sccb_header header;
 	u8 recognized[SCLP_CHP_INFO_MASK_SIZE];