Allow projects to define their own build.

To create a new project, add a directory under `project` and pass the
project name to `make`:

    mkdir project/my_project
    # Describe the build for the project.
    PROJECT=my_project make

Projects can be maintained separately from the main repository.

Change-Id: I33a9d7ca801e2fb3dd9795ece44577b3b565e913
diff --git a/inc/hf/layout.h b/inc/hf/layout.h
index 4c40223..9eabf4d 100644
--- a/inc/hf/layout.h
+++ b/inc/hf/layout.h
@@ -27,6 +27,12 @@
 paddr_t layout_data_begin(void);
 paddr_t layout_data_end(void);
 
+paddr_t layout_initrd_begin(void);
+paddr_t layout_initrd_end(void);
+
+paddr_t layout_fdt_begin(void);
+paddr_t layout_fdt_end(void);
+
 paddr_t layout_bin_end(void);
 
 paddr_t layout_primary_begin(void);