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>
diff --git a/arch/x86/cpu/intel_common/cpu.c b/arch/x86/cpu/intel_common/cpu.c
index 0fdef6f..ae42095 100644
--- a/arch/x86/cpu/intel_common/cpu.c
+++ b/arch/x86/cpu/intel_common/cpu.c
@@ -42,8 +42,10 @@
 	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));