drivers: thermal: tsens: Introduce IP-specific max_sensor count

The IP can support 'm' sensors while the platform can enable 'n' sensors
of the 'm' where n <= m.

Track maximum sensors supported by the IP so that we can correctly track
what subset of the sensors are supported on the platform.

Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>