serial: s5p: Remove common.h inclusion

It's not really needed here anymore. Remove it, as common.h is going
away at some point.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/drivers/serial/serial_s5p.c b/drivers/serial/serial_s5p.c
index fe52580..1772155 100644
--- a/drivers/serial/serial_s5p.c
+++ b/drivers/serial/serial_s5p.c
@@ -7,7 +7,6 @@
  * based on drivers/serial/s3c64xx.c
  */
 
-#include <common.h>
 #include <dm.h>
 #include <errno.h>
 #include <fdtdec.h>