drivers/serial/ns16550: move ifdef into Makefile COBJS-$(...)

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index b6fd0d7..0f980ab 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -28,10 +28,10 @@
 COBJS-$(CONFIG_ATMEL_USART) += atmel_usart.o
 COBJS-$(CONFIG_MCFUART) += mcfuart.o
 COBJS-$(CONFIG_NS9750_UART) += ns9750_serial.o
-COBJS-y += ns16550.o
+COBJS-$(CONFIG_SYS_NS16550) += ns16550.o
 COBJS-$(CONFIG_DRIVER_S3C4510_UART) += s3c4510b_uart.o
 COBJS-$(CONFIG_S3C64XX) += s3c64xx.o
-COBJS-y += serial.o
+COBJS-$(CONFIG_SYS_NS16550_SERIAL) += serial.o
 COBJS-$(CONFIG_IXP_SERIAL) += serial_ixp.o
 COBJS-$(CONFIG_MAX3100_SERIAL) += serial_max3100.o
 COBJS-$(CONFIG_PL010_SERIAL) += serial_pl01x.o