jtag: basic support for P&E Micro OSBDM (aka OSJTAG) adapter

This driver provides support for the P&E Micro OSBDM adapter (sometimes
named as OSJTAG), mounted on the Freescale TWRK60N512 bord. Thus, it
provides a quick start when working with this board. The driver doesn't
use BDM commands, but work with OSBDM adapter using only JTAG commands.

Change-Id: Ibc3779538e666e07651d3136431e5d44344f3b07
Signed-off-by: Jan Dakinevich <jan.dakinevich@gmail.com>
Reviewed-on: http://openocd.zylin.com/492
Tested-by: jenkins
Reviewed-by: Tomas Frydrych <tf+openocd@r-finger.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

tcl/interface/osbdm.cfg

@@ -0,0 +1,12 @@
+#
+# P&E Micro OSBDM (aka OSJTAG) interface
+#
+# http://pemicro.com/osbdm/
+#
+interface osbdm
+reset_config srst_only
+
+#
+# OSBDM doesn't support speed control
+#
+adapter_khz 1