drm/pan*: don't abuse current->group_leader

Cleanup and preparation to simplify the next changes.

Use current->tgid instead of current->group_leader->pid.

Link: https://lkml.kernel.org/r/aXY_0MrQBZWKbbmA@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Steven Price <steven.price@arm.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Christan König <christian.koenig@amd.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: oleg-nesterov

drivers/gpu/drm/panfrost/panfrost_gem.c

@@ -17,7 +17,7 @@
 static void panfrost_gem_debugfs_bo_add(struct panfrost_device *pfdev,
 					struct panfrost_gem_object *bo)
 {
-	bo->debugfs.creator.tgid = current->group_leader->pid;
+	bo->debugfs.creator.tgid = current->tgid;
 	get_task_comm(bo->debugfs.creator.process_name, current->group_leader);
 
 	mutex_lock(&pfdev->debugfs.gems_lock);

drivers/gpu/drm/panthor/panthor_gem.c

@@ -27,7 +27,7 @@ static void panthor_gem_debugfs_bo_add(struct panthor_gem_object *bo)
 	struct panthor_device *ptdev = container_of(bo->base.base.dev,
 						    struct panthor_device, base);
 
-	bo->debugfs.creator.tgid = current->group_leader->pid;
+	bo->debugfs.creator.tgid = current->tgid;
 	get_task_comm(bo->debugfs.creator.process_name, current->group_leader);
 
 	mutex_lock(&ptdev->gems.lock);