Thermal: kirkwood: Remove redundant use of of_match_ptr

'kirkwood_thermal_id_table' is always compiled in and the driver
is dependent on OF. Hence use of of_match_ptr is unnecessary.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Acked-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>