coresight: etm3x: fix inconsistencies with sysfs configuration

The current ETM3x configuration via sysfs can lead to the following
inconsistencies:

  - If a configuration is modified via sysfs while a perf session is
    active, the running configuration may differ between before
    a sched-out and after a subsequent sched-in.

To resolve these issues, separate the configuration into:

  - curr_config: the configuration applied to the current session
  - config: the configuration set via sysfs

Additionally:

  - Since curr_config and related fields are accessed only by the local CPU
    in etm_enable/disable_sysfs_smp_call() (similar to perf enable/disable),
    remove the lock/unlock from the sysfs enable/disable path and
    starting/dying_cpu path except when to access config fields only.

  - Some of sysfs interface read etm register directly. To reduce lock
    scope while the etm_enable_hw()/etm_disable_hw(), handle it via
    IPI so that registers could be read from on proper CPU.

Fixes: 1925a470ce69 ("coresight: etm3x: splitting struct etm_drvdata")
Tested-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Mike Leach <mike.leach@arm.com>
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20261003-separate_etm_cfg_v2-v13-5-5d8a29aead95@arm.com

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