[OG9, amdgcn, committed] Fix memory leak in libgomp
Committed to OG9 on behalf of Kwok ...
The list of struct gomp_threads allocated in gomp_gcn_enter_kernel was
not being freed in gomp_gcn_exit_kernel, leading to a small memory leak
every time a kernel is run. Runs with a lot of teams or many kernels
were running out of heap space.