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/arch/avr32/mm/init.c b/arch/avr32/mm/init.c
index 786de88..3c85fda 100644
--- a/arch/avr32/mm/init.c
+++ b/arch/avr32/mm/init.c
@@ -119,8 +119,7 @@
 		unsigned long zones_size[MAX_NR_ZONES];
 		unsigned long low, start_pfn;
 
-		start_pfn = pgdat->bdata->node_boot_start;
-		start_pfn >>= PAGE_SHIFT;
+		start_pfn = pgdat->bdata->node_min_pfn;
 		low = pgdat->bdata->node_low_pfn;
 
 		memset(zones_size, 0, sizeof(zones_size));