bootmem: replace node_boot_start in struct bootmem_data

Almost all users of this field need a PFN instead of a physical address,
so replace node_boot_start with node_min_pfn.

[Lee.Schermerhorn@hp.com: fix spurious BUG_ON() in mark_bootmem()]
Signed-off-by: Johannes Weiner <hannes@saeureba.de>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index 90921d10..4ddf292 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -28,7 +28,7 @@
  * memory pages (including holes) on the node.
  */
 typedef struct bootmem_data {
-	unsigned long node_boot_start;
+	unsigned long node_min_pfn;
 	unsigned long node_low_pfn;
 	void *node_bootmem_map;
 	unsigned long last_end_off;