x86/mce: Add a clear_bank() helper

x86/mce: Add a clear_bank() helper

Add a helper at the end of the MCA polling function to collect vendor and/or
feature actions.

Start with a basic skeleton for now. Actions for AMD thresholding and deferred
errors will be added later.

  [ bp: Drop the obvious comment too. ]

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/20250908-wip-mca-updates-v6-0-eef5d6c74b9c@amd.com