arm64: dts: imx8mm-venice-gw7901: remove unnecessary cpu temp override

Remove the unnecessary cpu_alert0 and cpu_crit0 TMU node overrides as
these are added dynamically by boot firmware based on CPU temperature
grade.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>