lima: fix NULL pointer dereference on error path in lima_context_destroy
When the following code path happens:
- drmSyncobjCreate: can fail here
- Thus ctx->pp_submit and ctx->gp_submit are NULL
- lima_submit_free: will access submit->in_sync_fd
It triggers a segfault in mesa because we are trying to derefence both ctx->pp_submit and ctx->gp_submit which are NULL.