thermal: broadcom: Add Stingray thermal driver

Stingray SoC has six temperature sensor and those are
configured, controlled and accessed to read temperature
and update in DDR memory using m0 firmware.
All six sensors has been given 4 bytes of memory in DDR
to write temperature in millivolts.

This thermal driver read temperature values from DDR
because no direct access to sensors.
Like this all temparature sensors are monitored and
trips at critical temperature.

If driver can't handle thermal runaways because of
any unknown reason, then firmware in m0 Processor
will handle.

Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Vikram Prakash <vikram.prakash@broadcom.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Pramod Kumar <pramod.kumar@broadcom.com>
Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>