add 'terminal program' functionality

This patch adds a 'cu' like serial terminal command to u-boot
using which you can access other serial ports from the system console.

OpenMoko uses this in their Neo1973 phones to get access to the GSM
Modem and GPS chip from the bootloader.

Signed-off-by: Harald Welte <laforge@openmoko.org>
diff --git a/common/Makefile b/common/Makefile
index 7be89a4..fbfa536 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -86,6 +86,7 @@
 COBJS-y += cmd_sata.o
 COBJS-$(CONFIG_CMD_SCSI) += cmd_scsi.o
 COBJS-$(CONFIG_CMD_SPI) += cmd_spi.o
+COBJS-$(CONFIG_CMD_TERMINAL) += cmd_terminal.o
 COBJS-$(CONFIG_CMD_UNIVERSE) += cmd_universe.o
 COBJS-$(CONFIG_CMD_USB) += cmd_usb.o
 COBJS-y += cmd_vfd.o