memory hotplug/s390: set phys_device

Implement arch specific arch_get_memory_phys_device function and
initialize phys_device for each memory section. That way we finally can
tell which piece of memory belongs to which physical device.

This makes s390's /sys/devices/system/memory/memoryX/phys_device display
the correct thing?

Signed-off-by: Heiko Carstens <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Gerald Schaefer <[e-mail]>
Cc: KAMEZAWA Hiroyuki <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/s390/char/sclp_cmd.c

···
 	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];