gpu: host1x: Check whether size of unpin isn't 0

Only gather pins are mapped by the Host1x driver, regular BO relocations
are not. Check whether size of unpin isn't 0, otherwise IOVA allocation at
0x0 could be erroneously released.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/host1x/job.c

@@ -569,7 +569,8 @@ void host1x_job_unpin(struct host1x_job *job)
 	for (i = 0; i < job->num_unpins; i++) {
 		struct host1x_job_unpin_data *unpin = &job->unpins[i];
 
-		if (!IS_ENABLED(CONFIG_TEGRA_HOST1X_FIREWALL) && host->domain) {
+		if (!IS_ENABLED(CONFIG_TEGRA_HOST1X_FIREWALL) &&
+		    unpin->size && host->domain) {
 			iommu_unmap(host->domain, job->addr_phys[i],
 				    unpin->size);
 			free_iova(&host->iova,