[IA64] Zero size /proc/vmcore on ia64

Set saved_max_pfn when discontig memory is in use.

This sets up saved_max_pfn when disctontig memory is in use.
This mirrors the code for contig memory.

This patch does not entirely solve the problem of making vmcore work,
however it does appear to be neccessary. Please consider applying.
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/mm/discontig.c

@@ -506,6 +506,12 @@ void __init find_memory(void)
 	max_pfn = max_low_pfn;
 
 	find_initrd();
+
+#ifdef CONFIG_CRASH_DUMP
+	/* If we are doing a crash dump, we still need to know the real mem
+	 * size before original memory map is reset. */
+        saved_max_pfn = max_pfn;
+#endif
 }
 
 #ifdef CONFIG_SMP