board: arc: em_starterkit*: fix OpenOCD configuration ftdi_device_desc
board: arc: em_starterkit*: fix OpenOCD configuration ftdi_device_desc

OpenOCD cofig command: ftdi_device_desc description provides the
USB device description (the iProduct string) of the adapter. And If not
specified, the device description is ignored during device selection.

In newer OpenOCD version from Zephyr's SDK v0.12, there are some
changes in OpenOCD scripts.
In file interface/ftdi/digilent-hs1.cfg, ftdi_device_desc will be set to
"Digilent Adept USB Device", while we get the iProduct string
"Digilent USB Device" from em_starterkit adapter.  it's better not
specify it and only use the vid and pid of the adapter for selection.

Signed-off-by: Watson Zeng <bb6a45ebfbb8932a11537002b062f5218879c562@synopsys.com>

zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,nashif/zephyr,nashif/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr