thermal: max77620: Add thermal driver for reporting junction temp

Maxim Semiconductor Max77620 supports alarm interrupts when
its die temperature crosses 120C and 140C. These threshold
temperatures are not configurable.

Add thermal driver to register PMIC die temperature as thermal
zone sensor and capture the die temperature warning interrupts
to notifying the client.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>