x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP

x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP

Intel and AMD have different CPUID bits hence for those use synthetic bits
which get set on the respective vendor's in init_speculation_control(). So
that debacles like what the commit message of

  c65732e4f721 ("x86/cpu: Restore CPUID_8000_0008_EBX reload")

talks about don't happen anymore.

Signed-off-by: Borislav Petkov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
Tested-by: Jörg Otte <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]