[IA64] Reserve elfcorehdr memory in CONFIG_CRASH_DUMP

IA64 kdump kernel failed to initialize /proc/vmcore in 2.6.28-rc2.
A bug was introduced in this patch commit:

  d9a9855d
  always reserve elfcore header memory in crash kernel

The problem was that the call to reserve_elfcorehdr() should be placed
in CONFIG_CRASH_DUMP rather than in CONFIG_CRASH_KERNEL, which does
not exist.
Signed-off-by: NJay Lan <jlan@sgi.com>
Acked-by: NSimon Hormon <horms@verge.net.au>
Signed-off-by: NTony Luck <tony.luck@intel.com>

arch/ia64/kernel/setup.c

@@ -359,7 +359,7 @@ reserve_memory (void)
 	}
 #endif
 
-#ifdef CONFIG_CRASH_KERNEL
+#ifdef CONFIG_CRASH_DUMP
 	if (reserve_elfcorehdr(&rsvd_region[n].start,
 			       &rsvd_region[n].end) == 0)
 		n++;