The QorIQ Layerscape SoC has several thermal sensors but the current
driver only supports one.

Massage the code to be sensor oriented and allow the support for
multiple sensors.
Signed-off-by: Yuantian Tang <andy.tang@nxp.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>