x86/cpuid: Only recalculate the shared feature bits once

x86/cpuid: Only recalculate the shared feature bits once

With accurate vendor information available, the shared bits can be sorted out
during recalculation, rather than at query time in the legacy cpuid path.

This means that:
 * Duplication can be dropped from the automatically generated cpuid data.
 * The toolstack need not worry about setting them appropriately.
 * They can be dropped from the system maximum featuresets.

While editing gen-cpuid.py, reflow some comments which exceeded the expected
line length.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>