coresight: add module license

coresight: add module license

When built as a loadable module, coresight now causes a warning about
missing license information.

WARNING: modpost: missing MODULE_LICENSE() in drivers/hwtracing/coresight/coresight.o

Fixes: 8e264c52e1da ("coresight: core: Allow the coresight core driver to be built as a module")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20201026160205.3704789-1-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>