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/spl.c b/arch/x86/cpu/apollolake/spl.c
index b351d73..510f8c4 100644
--- a/arch/x86/cpu/apollolake/spl.c
+++ b/arch/x86/cpu/apollolake/spl.c
@@ -116,7 +116,7 @@
 		return ret;
 
 	spl_image->size = CONFIG_SYS_MONITOR_LEN;  /* We don't know SPL size */
-	spl_image->entry_point = spl_phase() == PHASE_TPL ?
+	spl_image->entry_point = xpl_phase() == PHASE_TPL ?
 		CONFIG_SPL_TEXT_BASE : CONFIG_TEXT_BASE;
 	spl_image->load_addr = spl_image->entry_point;
 	spl_image->os = IH_OS_U_BOOT;