xpl: Rename spl_next_phase() and spl_prev_phase()

Rename this to use the xpl prefix.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index ab05419..6276b27 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -1676,7 +1676,7 @@
 	 * not whether this phase creates one.
 	 */
 	if (CONFIG_IS_ENABLED(BLOBLIST) &&
-	    (spl_prev_phase() != PHASE_TPL ||
+	    (xpl_prev_phase() != PHASE_TPL ||
 	     !IS_ENABLED(CONFIG_TPL_BLOBLIST))) {
 		ret = bloblist_maybe_init();
 		if (!ret) {