bootm: Set working fdt address as part of the bootm flow

Set the fdt working address so "fdt FOO" commands can be used as part
of the bootm flow.  Also set an the environment variable "fdtaddr"
with the value.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/include/fdt_support.h b/include/fdt_support.h
index f2f2cd5..f14ab68 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -68,5 +68,7 @@
 void ft_pci_setup(void *blob, bd_t *bd);
 #endif
 
+void set_working_fdt_addr(void *addr);
+
 #endif /* ifdef CONFIG_OF_LIBFDT */
 #endif /* ifndef __FDT_SUPPORT_H */