x86/MCE/AMD: Allow thresholding interface updates after init

commit 1f52b0ab upstream.

Changes to the AMD Thresholding sysfs code prevents sysfs writes from
updating the underlying registers once CPU init is completed, i.e.
"threshold_banks" is set.

Allow the registers to be updated if the thresholding interface is
already initialized or if in the init path. Use the "set_lvt_off" value
to indicate if running in the init path, since this value is only set
during init.

Fixes: a037f3ca

 ("x86/mce/amd: Make threshold bank setting hotplug robust")
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220117161328.19148-1-yazen.ghannam@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>