thermal: MAINTAINERS: Add git tree path for SoC specific updates

To reduce thermal maintenance load on Rui, SoC specific patches would be
applied by me now. Rui Zhang will pull in these changes from time to time (at
rc's). Additionally I would be sending him pull request for every merge
window and rc's (for fixes).

Branch names would be: next and fixes.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>