85xx: Introduce determine_mp_bootpg() helper.

Match determine_mp_bootpg() that was added for 86xx.  We need this to
address a bug introduced in v2009.03 with 86xx MP booting.  We have to
make sure to reserve the region of memory used for the MP bootpg() so
other u-boot code doesn't use it.

Also added a comment about how cpu_reset() is dealing w/an errata on
early 85xx MP HW.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/cpu/mpc85xx/fdt.c b/cpu/mpc85xx/fdt.c
index 2d36c24..26a8f48 100644
--- a/cpu/mpc85xx/fdt.c
+++ b/cpu/mpc85xx/fdt.c
@@ -39,13 +39,8 @@
 {
 	int off;
 	ulong spin_tbl_addr = get_spin_addr();
-	u32 bootpg, id = get_my_id();
-
-	/* if we have 4G or more of memory, put the boot page at 4Gb-4k */
-	if ((u64)gd->ram_size > 0xfffff000)
-		bootpg = 0xfffff000;
-	else
-		bootpg = gd->ram_size - 4096;
+	u32 bootpg = determine_mp_bootpg();
+	u32 id = get_my_id();
 
 	off = fdt_node_offset_by_prop_value(blob, -1, "device_type", "cpu", 4);
 	while (off != -FDT_ERR_NOTFOUND) {