x86: Wrap print_ch() with config option

print_ch() should not be used if DEBUG_UART is off.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/x86_64/cpu.c b/arch/x86/cpu/x86_64/cpu.c
index 77cbb56..db171f7 100644
--- a/arch/x86/cpu/x86_64/cpu.c
+++ b/arch/x86/cpu/x86_64/cpu.c
@@ -31,7 +31,9 @@
 	 *
 	 * U-Boot SPL 2017.01
 	 */
+#ifdef CONFIG_DEBUG_UART
 	printch(' ');
+#endif
 }
 
 int cpu_has_64bit(void)