hte: Add Tegra194 HTE kernel provider

Tegra194 device has multiple HTE instances also known as GTE (Generic
Hardware Timestamping Engine) which can timestamp subset of SoC lines
and signals. This provider driver focuses on IRQ and GPIO lines and
exposes timestamping ability on those lines to the consumers through
HTE subsystem.

Also, with this patch, added:
- documentation about this provider and its capabilities at
Documentation/hte.
- Compilation support in Makefile and Kconfig

Signed-off-by: Dipen Patel <dipenp@nvidia.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>