soc: qcom: rpmhpd: Remove mx/cx relationship on sc7280

The requirement to specify the active + sleep and active-only MX
power-domains as the parents of the corresponding CX power domains is
not applicable on sc7280. Fix it by using the cx/cx_ao structs for
sc7280 instead of the _w_mx_parent ones.

Signed-off-by: Rajendra Nayak <quic_rjendra@quicinc.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/1639063917-9011-4-git-send-email-quic_rjendra@quicinc.com