[PATCH] ia64: fix min_low_pfn/max_low_pfn build errors

[Randy Dunlap]

Fix min_low_pfn/max_low_pfn build errors for arch/ia64/: (e.g.)

 ERROR: "max_low_pfn" [drivers/rpmsg/virtio_rpmsg_bus.ko] undefined!
 ERROR: "min_low_pfn" [drivers/rpmsg/virtio_rpmsg_bus.ko] undefined!
 ERROR: "min_low_pfn" [drivers/hwtracing/intel_th/intel_th_msu.ko] undefined!
 ERROR: "max_low_pfn" [drivers/hwtracing/intel_th/intel_th_msu.ko] undefined!
 ERROR: "min_low_pfn" [drivers/crypto/cavium/nitrox/n5pf.ko] undefined!
 ERROR: "max_low_pfn" [drivers/crypto/cavium/nitrox/n5pf.ko] undefined!
 ERROR: "max_low_pfn" [drivers/md/dm-integrity.ko] undefined!
 ERROR: "min_low_pfn" [drivers/md/dm-integrity.ko] undefined!
 ERROR: "max_low_pfn" [crypto/tcrypt.ko] undefined!
 ERROR: "min_low_pfn" [crypto/tcrypt.ko] undefined!
 ERROR: "min_low_pfn" [security/keys/encrypted-keys/encrypted-keys.ko] undefined!
 ERROR: "max_low_pfn" [security/keys/encrypted-keys/encrypted-keys.ko] undefined!
 ERROR: "min_low_pfn" [arch/ia64/kernel/mca_recovery.ko] undefined!
 ERROR: "max_low_pfn" [arch/ia64/kernel/mca_recovery.ko] undefined!

David suggested just exporting min_low_pfn & max_low_pfn in
mm/memblock.c:
https://lore.kernel.org/lkml/alpine.DEB.2.22.394.2006291911220.1118534@xxxxxxxxxxxxxxxxxxxxxxxxx/

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: linux-ia64@xxxxxxxxxxxxxxx
---
 arch/ia64/kernel/ia64_ksyms.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-next-20200825.orig/arch/ia64/kernel/ia64_ksyms.c
+++ linux-next-20200825/arch/ia64/kernel/ia64_ksyms.c
@@ -3,7 +3,7 @@
  * Architecture-specific kernel symbols
  */
 
-#ifdef CONFIG_VIRTUAL_MEM_MAP
+#if defined(CONFIG_VIRTUAL_MEM_MAP) || defined(CONFIG_DISCONTIGMEM)
 #include <linux/compiler.h>
 #include <linux/export.h>
 #include <linux/memblock.h>