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

During imx_thermal probe we have the following log:

[    1.514819] imx_thermal 2000000.aips-bus:tempmon: failed to register cpufreq cooling device: -517
[    1.515064] platform 2000000.aips-bus:tempmon: Driver imx_thermal requests probe deferral

Avoid printing the error message in the EPROBE_DEFER case.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>