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/ti/evm/evm.c b/board/ti/evm/evm.c
index d0b9baf..d26dd5b 100644
--- a/board/ti/evm/evm.c
+++ b/board/ti/evm/evm.c
@@ -15,6 +15,7 @@
 #include <env.h>
 #include <ns16550.h>
 #include <netdev.h>
+#include <serial.h>
 #include <asm/io.h>
 #include <asm/arch/mem.h>
 #include <asm/arch/mux.h>