x86,fs/resctrl: Add an architectural hook called for first mount

x86,fs/resctrl: Add an architectural hook called for first mount

Enumeration of Intel telemetry events is an asynchronous process involving
several mutually dependent drivers added as auxiliary devices during the
device_initcall() phase of Linux boot. The process finishes after the probe
functions of these drivers completes. But this happens after
resctrl_arch_late_init() is executed.

Tracing the enumeration process shows that it does complete a full seven
seconds before the earliest possible mount of the resctrl file system (when
included in /etc/fstab for automatic mount by systemd).

Add a hook for use by telemetry event enumeration and initialization and
run it once at the beginning of resctrl mount without any locks held.
The architecture is responsible for any required locking.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20260105191711.GBaVwON5nZn-uO6Sqg@fat_crate.local