arm: add uart dcc support

Serial driver via the EmbeddedICE macrocell's DCC channel using
co-processor 14.

It does include a timeout to ensure that the system does not
totally freeze when there is nothing connected to read.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/lib_arm/board.c b/lib_arm/board.c
index f125d38..09eaaf2 100644
--- a/lib_arm/board.c
+++ b/lib_arm/board.c
@@ -145,6 +145,9 @@
  * but let's get it working (again) first...
  */
 
+#if defined(CONFIG_ARM_DCC) && !defined(CONFIG_BAUDRATE)
+#define CONFIG_BAUDRATE 115200
+#endif
 static int init_baudrate (void)
 {
 	char tmp[64];	/* long enough for environment variables */