jtag/drivers/cmsis_dap: fix check for hardcoded vids/pids

jtag/drivers/cmsis_dap: fix check for hardcoded vids/pids

This is intended to fix cmsis_dap_vid_pid command but it doesn't
because cmsis-dap has only one transport and it's auto-selected from
"interface" command handler (before any other commands are run) and as
the result cmsis_dap_usb_open() is called too early.

Change-Id: Idaade73797d8df67a6439d096f6abc9736495599
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/2191
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>