imx: imx8m: Imply IMX_TMU

imx: imx8m: Imply IMX_TMU

If the CPU Information is displayed from imx8_cpu, it displays the
cpu temperature grade and operating temperature if CONFIG_IMX9 is
defined. This behavior is similar to what happens mach-imx/cpu.c,
except that the latter checks for IMX_THERMAL or IMX_TMU.

In preparation to make imx8_cpu act like the previous implementation
for any CPU, make IMX8M imply IMX_TMU so it will be always displayed
unless a user decides to disable it.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>