drivers: thermal: tsens: Add critical interrupt support

TSENS IP v2.x adds critical threshold interrupt support for each sensor
in addition to the upper/lower threshold interrupt. Add support in the
driver.

While the critical interrupts themselves aren't currently used by Linux,
the HW line is also used by the TSENS watchdog. So this patch acts as
infrastructure to enable watchdog functionality for the TSENS IP.

Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/51b22461d4b5f85a817274568459db4579fd4298.1584015867.git.amit.kucheria@linaro.org