Allow architecture-specific memory reservation

All memory to be reserved for use after relocation by adding a new call
to perform this reservation.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/board_f.c b/common/board_f.c
index 3a4b32c..215108b 100644
--- a/common/board_f.c
+++ b/common/board_f.c
@@ -807,6 +807,12 @@
 	return 0;
 }
 
+/* Architecture-specific memory reservation */
+__weak int reserve_arch(void)
+{
+	return 0;
+}
+
 static init_fnc_t init_sequence_f[] = {
 #ifdef CONFIG_SANDBOX
 	setup_ram_buf,
@@ -970,6 +976,7 @@
 	setup_machine,
 	reserve_global_data,
 	reserve_fdt,
+	reserve_arch,
 	reserve_stacks,
 	setup_dram_config,
 	show_dram_config,