x86/cpuid: Extend the cpuid= option to support all named features

x86/cpuid: Extend the cpuid= option to support all named features

For gen-cpuid.py, fix a comment describing self.names, and generate the
reverse mapping in self.values.  Write out INIT_FEATURE_NAMES which maps a
string name to a bit position.

For parse_cpuid(), use cmdline_strcmp() and perform a binary search over
INIT_FEATURE_NAMES.  A tweak to cmdline_strcmp() is needed to break at equals
signs as well.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>