arm64: dts: qcom: sc8280xp: Add epss_l3 node

Add a device node for the EPSS L3 frequency domain.

Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Tested-by: Steev Klimaszewski <steev@kali.org>
Reviewed-by: Sibi Sankar <quic_sibis@quicinc.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221111032515.3460-8-quic_bjorande@quicinc.com