drm/imagination: Free pvr_vm_gpuva after unlink

This caused a measurable memory leak. Although the individual
allocations are small, the leaks occurs in a high-usage codepath
(remapping or unmapping device memory) so they add up quickly.

Fixes: ff5f643de0 ("drm/imagination: Add GEM and VM related code")
Cc: stable@vger.kernel.org
Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Link: https://patchwork.freedesktop.org/patch/msgid/35867394-d8ce-4698-a8fd-919a018f1583@imgtec.com
Signed-off-by: Matt Coster <matt.coster@imgtec.com>

drivers/gpu/drm/imagination/pvr_vm.c

@@ -114,6 +114,8 @@ struct pvr_vm_gpuva {
 	struct drm_gpuva base;
 };
 
+#define to_pvr_vm_gpuva(va) container_of_const(va, struct pvr_vm_gpuva, base)
+
 enum pvr_vm_bind_type {
 	PVR_VM_BIND_TYPE_MAP,
 	PVR_VM_BIND_TYPE_UNMAP,
@@ -386,6 +388,7 @@ pvr_vm_gpuva_unmap(struct drm_gpuva_op *op, void *op_ctx)
 
 	drm_gpuva_unmap(&op->unmap);
 	drm_gpuva_unlink(op->unmap.va);
+	kfree(to_pvr_vm_gpuva(op->unmap.va));
 
 	return 0;
 }
@@ -433,6 +436,7 @@ pvr_vm_gpuva_remap(struct drm_gpuva_op *op, void *op_ctx)
 	}
 
 	drm_gpuva_unlink(op->remap.unmap->va);
+	kfree(to_pvr_vm_gpuva(op->remap.unmap->va));
 
 	return 0;
 }