arm64: dts: remove cpu compatible "arm,armv8" for s4

Amlogic s4 device is already applied, but cpu compatible 'arm,armv8'
is only valid for software models, so we remove it.

Fixes: ac4dfd0d ("arm64: dts: add support for S4 based Amlogic AQ222")
Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20220408070901.26446-1-xianwei.zhao@amlogic.com