drm/ttm/tests: Correct modules' licenses

The test files are GPL and MIT, so update the definitions accordingly.

Signed-off-by: Karolina Stolarek <karolina.stolarek@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/54cd7289db67ec396b67ef48dbb45521d56ec03c.1718192625.git.karolina.stolarek@intel.com