coresight: etm4x: fix inconsistencies with sysfs configuration

The current ETM4x configuration via sysfs can lead to
several inconsistencies:

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

  - If a perf session and a sysfs session enable tracing concurrently,
    the configuration from configfs may become corrupted.

  - There is a risk of corrupting drvdata->config if a perf session enables
    tracing while cscfg_csdev_disable_active_config() is being handled in
    etm4_disable_sysfs().

To resolve these issues, separate the configuration into:

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

Additionally:

  - Apply the configuration from configfs after taking the appropriate
    mode.

  - Since curr_config and related fields are accessed only by the local CPU
    in etm4_enable/disable_sysfs_smp_call() (similar to perf enable/disable),
    remove the lock/unlock from the sysfs enable/disable path and
    startup/dying_cpu except when to access config fields.

As the curr_config is used for cfg-configfs, etmv4 doesn't need to set
its lock for the cfg-configfs since the curr_config is proceted by cs_mode
otherwise it would make a possible cpu-stall when it get interrupt while
setting the sysfs configuration.

Therefore, set the drv_spinlock for cfg-configfs as NULL and
let the cfg-configfs disable irq without grap drv_spinlock when it is NULL.

Fixes: 54ff892b76c6 ("coresight: etm4x: splitting struct etmv4_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-v13-4-5d8a29aead95@arm.com

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