fs/resctrl: Provide interface to update the event configurations

When "mbm_event" counter assignment mode is enabled, users can modify the
event configuration by writing to the 'event_filter' resctrl file.  The event
configurations for mbm_event mode are located in
/sys/fs/resctrl/info/L3_MON/event_configs/.

Update the assignments of all CTRL_MON and MON resource groups when the event
configuration is modified.

Example:
  $ mount -t resctrl resctrl /sys/fs/resctrl

  $ cd /sys/fs/resctrl/

  $ cat info/L3_MON/event_configs/mbm_local_bytes/event_filter
    local_reads,local_non_temporal_writes,local_reads_slow_memory

  $ echo "local_reads,local_non_temporal_writes" >
    info/L3_MON/event_configs/mbm_total_bytes/event_filter

  $ cat info/L3_MON/event_configs/mbm_total_bytes/event_filter
    local_reads,local_non_temporal_writes

Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com