board_f: Move fdt_size to board

This value is only really used before relocation. There is not much use
to showing its value in bdinfo, so drop it. Move it to the new boardf
struct.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/asm-generic/global_data.h

@@ -226,10 +226,6 @@ struct global_data {
 	 * @fdt_blob: U-Boot's own device tree, NULL if none
 	 */
 	const void *fdt_blob;
-	/**
-	 * @fdt_size: space reserved for relocated device space
-	 */
-	unsigned long fdt_size;
 	/**
 	 * @fdt_src: Source of FDT
 	 */