ARM: imx: novena: Enable DM thermal

Enable DM thermal driver and iMX thermal driver to get accurate
CPU frequency reporting in the boot log.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Vagrant Cascadian <vagrant@debian.org>