Add a simple infrastructure for setting, resetting and querying
platform feature flags.

Flags can be either global or architecture specific.
Signed-off-by: NJuergen Gross <jgross@suse.com>
Reviewed-by: NOleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64 only
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NBorislav Petkov <bp@suse.de>
Signed-off-by: NJuergen Gross <jgross@suse.com>