thermal: qoriq: add thermal monitor unit version 2 support

Thermal Monitor Unit v2 is introduced on new Layscape SoC.
Compared to v1, TMUv2 has a little different register layout
and digital output is fairly linear.

Signed-off-by: Yuantian Tang <andy.tang@nxp.com>
Reviewed-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20191011020534.334-1-andy.tang@nxp.com