x86/resctrl: Introduce resctrl_file_fflags_init() to initialize fflags

x86/resctrl: Introduce resctrl_file_fflags_init() to initialize fflags

thread_throttle_mode_init() and mbm_config_rftype_init() both initialize
fflags for resctrl files.

Adding new files will involve adding another function to initialize
the fflags. This can be simplified by adding a new function
resctrl_file_fflags_init() and passing the file name and flags
to be initialized.

Consolidate fflags initialization into resctrl_file_fflags_init() and
remove thread_throttle_mode_init() and mbm_config_rftype_init().

  [ Tony: Drop __init attribute so resctrl_file_fflags_init() can be used at
    run time. ]

Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/r/20241206163148.83828-2-tony.luck@intel.com