thermal: imx: Remove unused includes

Remove unused includes to simplify the code.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1583762668-12099-1-git-send-email-Anson.Huang@nxp.com