arm64: dts: qcom: sc8280xp: Vote for CX in USB controllers

Running GCC_USB30_*_MASTER_CLK at 200MHz requires CX at nominal level,
not doing so results in occasional lockups. This was previously hidden
by the fact that the display stack incorrectly voted for CX (instead of
MMCX).

Fixes: 152d1faf ("arm64: dts: qcom: add SC8280XP platform")
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230112135117.3836655-1-quic_bjorande@quicinc.com