thermal/drivers/renesas/rzg3e: Fix add thermal driver for the Renesas RZ/G3E SoC

When applied the change commit 19d3a40, a conflict appeared
resulting into a manual fix. However the new file rzg3e_thermal.c was
not added but stayed locally in source tree and miss to be merged with
the entire change.

Fix this by adding the file back.

Fixes: 19d3a40 ("Add thermal driver for the Renesas RZ/G3E SoC")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202509272225.sARVqv2G-lkp@intel.com
Signed-off-by: John Madieu <john.madieu.xa@bp.renesas.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

Author: John Madieu