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>

include/devices.h

@@ -98,6 +98,9 @@ struct list_head* device_get_list(void);
 device_t* device_get_by_name(char* name);
 device_t* device_clone(device_t *dev);
 
+#ifdef CONFIG_ARM_DCC_MULTI
+int drv_arm_dcc_init(void);
+#endif
 #ifdef CONFIG_LCD
 int	drv_lcd_init (void);
 #endif