jtag: drivers: provide initial support for usb path filtering

jtag: drivers: provide initial support for usb path filtering

With this patch drivers will be able to use usb path filtering.
The path format is identical to the format provided by linux kernel:
bus-port.port....
With this format it should be easier just to copy and paste
path found in dmesg.

Change-Id: I8bafa6fcb7a66ff68cc961a376f97f4f3dee35aa
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-on: http://openocd.zylin.com/4580
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>