Avoid pointer type value compared with 0 to make code clear.
Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1647484953-15249-1-git-send-email-baihaowen@meizu.com