thermal: db8500: Do not print error message in the EPROBE_DEFER case

Avoid printing the error message in the EPROBE_DEFER case
where registering cpu cooling at db8500 thermal driver.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: devicetree@vger.kernel.org
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>