Revert "global_data: Drop spl_handoff"

This breaks chromebook_coral which says:

   Video: No video mode configured in FSP!

This reverts commit 2e9313179a.

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

include/asm-generic/global_data.h

@@ -400,6 +400,12 @@ struct global_data {
 	 */
 	struct bloblist_hdr *bloblist;
 #endif
+#if CONFIG_IS_ENABLED(HANDOFF)
+	/**
+	 * @spl_handoff: SPL hand-off information
+	 */
+	struct spl_handoff *spl_handoff;
+#endif
 #if defined(CONFIG_TRANSLATION_OFFSET)
 	/**
 	 * @translation_offset: optional translation offset