x86: kconfig: Select ARCH_EARLY_INIT_R in the platform Kconfig

This is architecture-dependent early initialization hence should
be put in the platform Kconfig.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/broadwell/refcode.c b/arch/x86/cpu/broadwell/refcode.c
index 436c6c4..4fa4de3 100644
--- a/arch/x86/cpu/broadwell/refcode.c
+++ b/arch/x86/cpu/broadwell/refcode.c
@@ -56,7 +56,17 @@
 	uint32_t padding[4];
 } __packed;
 
-int cpu_run_reference_code(void)
+/**
+ * cpu_run_reference_code() - Run the platform reference code
+ *
+ * Some platforms require a binary blob to be executed once SDRAM is
+ * available. This is used to set up various platform features, such as the
+ * platform controller hub (PCH). This function should be implemented by the
+ * CPU-specific code.
+ *
+ * @return 0 on success, -ve on failure
+ */
+static int cpu_run_reference_code(void)
 {
 	struct pei_data _pei_data __aligned(8);
 	struct pei_data *pei_data = &_pei_data;
@@ -111,3 +121,8 @@
 
 	return 0;
 }
+
+int arch_early_init_r(void)
+{
+	return cpu_run_reference_code();
+}