xpl: Rename spl_phase() to xpl_phase()

Rename this function to indicate that it refers to any xPL phase.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/apollolake/lpc.c b/arch/x86/cpu/apollolake/lpc.c
index 531ff1c..f34c199 100644
--- a/arch/x86/cpu/apollolake/lpc.c
+++ b/arch/x86/cpu/apollolake/lpc.c
@@ -80,7 +80,7 @@
 
 		lgir_reg_num = find_unused_pmio_window();
 		if (lgir_reg_num < 0) {
-			if (spl_phase() > PHASE_TPL) {
+			if (xpl_phase() > PHASE_TPL) {
 				log_err("LPC: Cannot open IO window: %lx size %lx\n",
 					bridge_base, size - bridged_size);
 				log_err("No more IO windows\n");