binman: Allow setting the ROM offset

On x86 the SPI ROM can be memory-mapped, at least most of it. Add a way
to tell binman the offset from a ROM address to a RAM address.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/binman.h

@@ -20,6 +20,14 @@ struct binman_entry {
 	u32 size;
 };
 
+/**
+ * binman_set_rom_offset() - Set the ROM memory-map offset
+ *
+ * @rom_offset: Offset from an image_pos to the memory-mapped address. This
+ *	tells binman that ROM image_pos x can be addressed at rom_offset + x
+ */
+void binman_set_rom_offset(int rom_offset);
+
 /**
  * binman_entry_find() - Find a binman symbol
  *