thermal: imx8mm: Add i.MX8MP support

i.MX8MP shares same TMU with i.MX8MM, the only difference is i.MX8MP
has two thermal sensors while i.MX8MM ONLY has one, add multiple sensors
support for i.MX8MM TMU driver.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1584674791-9717-2-git-send-email-Anson.Huang@nxp.com