MAINTAINERS: thermal: Add Daniel Lezcano as the thermal maintainer

Add Daniel Lezcano as the co-maintainer of thermal subsystem.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20191205115150.18836-1-rui.zhang@intel.com