thermal: Add Tegra BPMP thermal sensor driver

On Tegra186, the BPMP (Boot and Power Management Processor) exposes an
interface to thermal sensors on the system-on-chip. This driver
implements access to the interface. It supports reading the
temperature, setting trip points and receiving notification of a
tripped trip point.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>