coresight: etm4x: Set skip_power_up in etm4_init_arch_data function

skip_power_up is used in etm4_init_arch_data when set lpoverride. So
need to set the value of it before calling using it.

Fixes: 5214b563 ("coresight: etm4x: Add support for sysreg only devices")
Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20240131105423.9519-1-quic_jinlmao@quicinc.com