[IA64] fix show_mem for VIRTUAL_MEM_MAP+FLATMEM

contig.c (FLATMEM) requires the same optimization as in discontig.c for show_mem
when VIRTUAL_MEM_MAP is in use. Otherwise FLATMEM has softlockup timeouts.
This was boot tested for memory configuration: SPARSEMEM,
DISCONTIG+VIRTUAL_MEM_MAP, FLATMEM, FLATMEM+VIRTUAL_MEM_MAP and
FLATMEM+VIRTUAL_MEM_MAP with largest memory gap less than LARGE_GAP by
using boot parameter "mem=".

This was boot tested and "echo m >/proc/sysrq-trigger" output evaluated for
: FLATMEM, FLATMEM+VIRTUAL_MEM_MAP, DISCONTIGMEM+VIRTUAL_MEM_MAP and
SPARSEMEM.

Signed-off-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/include/asm-ia64/meminit.h b/include/asm-ia64/meminit.h
index 894bc4d..6a33a07 100644
--- a/include/asm-ia64/meminit.h
+++ b/include/asm-ia64/meminit.h
@@ -56,6 +56,11 @@
   extern struct page *vmem_map;
   extern int find_largest_hole (u64 start, u64 end, void *arg);
   extern int create_mem_map_page_table (u64 start, u64 end, void *arg);
+  extern int vmemmap_find_next_valid_pfn(int, int);
+#else
+static inline int vmemmap_find_next_valid_pfn(int node, int i)
+{
+	return i + 1;
+}
 #endif
-
 #endif /* meminit_h */