package/tslib: update upstream source address
The project has been moved from the kergoth user account to the
libts organisation on github. While github seems to maintain redirects,
we should use the new location directly.
Signed-off-by: Martin Kepplinger <martin.kepplinger@ginzinger.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>