x86: Add debugging when a microcode update fails

Add a debug() at this point to help figure out what is wrong.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heiko Schocher<hs@denx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/intel_common/cpu.c

@@ -42,8 +42,10 @@ int cpu_common_init(void)
 	enable_lapic();
 
 	ret = microcode_update_intel();
-	if (ret && ret != -EEXIST)
+	if (ret && ret != -EEXIST) {
+		debug("%s: Microcode update failure (err=%d)\n", __func__, ret);
 		return ret;
+	}
 
 	/* Enable upper 128bytes of CMOS */
 	writel(1 << 2, RCB_REG(RC));