fs/resctrl: Introduce event configuration field in struct mon_evt

fs/resctrl: Introduce event configuration field in struct mon_evt

When supported, mbm_event counter assignment mode allows the user to configure
events to track specific types of memory transactions.

Introduce an evt_cfg field in struct mon_evt to define the type of memory
transactions tracked by a monitoring event. Also add a helper function to get
the evt_cfg value.

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