ns16550: zap CONFIG_NS16550_SERIAL

Zap CONFIG_NS16550_SERIAL, as the unification of ns16550 drivers
is completed.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/sunxi-common.h b/include/configs/sunxi-common.h
index f560219..7a4853c 100644
--- a/include/configs/sunxi-common.h
+++ b/include/configs/sunxi-common.h
@@ -45,9 +45,7 @@
 #define CONFIG_SYS_NS16550_SERIAL
 /* ns16550 reg in the low bits of cpu reg */
 #define CONFIG_SYS_NS16550_CLK		24000000
-#ifdef CONFIG_DM_SERIAL
-# define CONFIG_NS16550_SERIAL
-#else
+#ifndef CONFIG_DM_SERIAL
 # define CONFIG_SYS_NS16550_REG_SIZE	-4
 # define CONFIG_SYS_NS16550_COM1		SUNXI_UART0_BASE
 # define CONFIG_SYS_NS16550_COM2		SUNXI_UART1_BASE