cpuidle: psci: Drop redundant assignment of CPUIDLE_FLAG_RCU_IDLE

When using the hierarchical topology and PSCI OSI-mode we may end up
overriding the deepest idle-state's ->enter|enter_s2idle() callbacks, but
there is no point to also re-assign the CPUIDLE_FLAG_RCU_IDLE for the
idle-state in question, as that has already been set when parsing the
states from DT. See init_state_node().

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Raghavendra Kakarla <quic_rkakarla@quicinc.com>  # qcm6490 with PREEMPT_RT set
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240527142557.321610-6-ulf.hansson@linaro.org