drm/amdkfd: CRIU fixes

Instead of trying to use close_fd() on failure exits, just have
criu_get_prime_handle() store the file reference without inserting
it into descriptor table.

Then, once the callers are past the last failure exit, they can go
and either insert all those file references into the corresponding
slots of descriptor table, or drop all those file references and
free the unused descriptors.

Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>