drivers: xds110: Add support of alternate XDS110 configurations

drivers: xds110: Add support of alternate XDS110 configurations

The XDS110 supports alternate configurations, each of which has
a unique vid/pid:

0451/bef3 -- Standard (legacy) configuration
0451/bef4 -- Drag-n-Drop configuration
1cbe/02a5 -- CMSIS-DAP 2.0 on BULK interface configuration

It's not important to OpenOCD what the differences are except
that OpenOCD needs to know how to connect using the different
vid/pids and, in the case of the last one, use a different
interface for the debug connection.

Updated the XDS110 source to search for all possible
configurations, and updated the udev rules file to enable
user access to the alternate configuraitons.

For the curious, you can download the latest XDS emupack from
software-dl.ti.com/ccs/esd/documents/xdsdebugprobes/emu_xds_software_package_download.html
Install to an empty directory, and documentation for the
XDS110 is located in the .../ccs_base/common/uscif/xds110
of the installation.

Updated for comments in code review. Changed const variable
names to lower case. Reworked interface/endpoint setting
to use arrays suggestion.

Change-Id: Icc9d11c6618f43d87ae8171c78ebf238800d3ac2
Signed-off-by: Edward Fewell <efewell@ti.com>
Reviewed-on: http://openocd.zylin.com/5494
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>