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>
diff --git a/drivers/gpu/host1x/job.c b/drivers/gpu/host1x/job.c
index e2f4a4d..527a1cd 100644
--- a/drivers/gpu/host1x/job.c
+++ b/drivers/gpu/host1x/job.c
@@ -569,7 +569,8 @@
 	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,