common: Move serial functions out of common.h

These functions belong in serial.h so move them over.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/board/logicpd/am3517evm/am3517evm.c b/board/logicpd/am3517evm/am3517evm.c
index 95c4cfc..18f3c3f 100644
--- a/board/logicpd/am3517evm/am3517evm.c
+++ b/board/logicpd/am3517evm/am3517evm.c
@@ -13,6 +13,7 @@
 #include <common.h>
 #include <dm.h>
 #include <ns16550.h>
+#include <serial.h>
 #include <asm/io.h>
 #include <asm/omap_musb.h>
 #include <asm/arch/am35x_def.h>