arm64: dts: sdm845: Remove per-CPU thermal zones

The cpufreq cooling devices have been removed by

  52e3b2ca ("arm64: dts: qcom: sdm845: Remove cpufreq cooling devices for CPU thermal zones")

but the per-CPU thermal zones remain. Per monitor_thermal_zone(), we get
one polling workqueue per TZ, which is a lot of noise considering the only
time those thermal zones will affect the system will be upon crossing a
critical trip point.

Remove the per-CPU thermal zones and let the cluster-wide ones handle
critical temperature trip points.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>