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/broadwell/cpu.c b/arch/x86/cpu/broadwell/cpu.c
index dc6717e..8746374 100644
--- a/arch/x86/cpu/broadwell/cpu.c
+++ b/arch/x86/cpu/broadwell/cpu.c
@@ -68,7 +68,7 @@
 	post_code(POST_CPU_INIT);
 
 	/* Do a mini-init if TPL has already done the full init */
-	if (IS_ENABLED(CONFIG_TPL) && spl_phase() != PHASE_TPL)
+	if (IS_ENABLED(CONFIG_TPL) && xpl_phase() != PHASE_TPL)
 		return x86_cpu_reinit_f();
 	else
 		return x86_cpu_init_f();