arm64: dts: qcom: msm8998-clamshell: Remove retention idle state

The retention idle state does not appear to be supported by the firmware
present on the msm8998 laptops since the state is advertised as disabled
in ACPI, and attempting to enable the state in DT is observed to result
in boot hangs.  Therefore, remove the state from use to address the
observed issues.

Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Fixes: 2c6d2d3a (arm64: dts: qcom: Add Lenovo Miix 630)
Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>