i386: cpu: eliminate duplicate feature names

i386: cpu: eliminate duplicate feature names

Instead of having duplicate feature names on the ext2_feature array for
the AMD feature bit aliases, we keep the feature names only on the
feature_name[] array, and copy the corresponding bits to
cpuid_ext2_features in case the CPU vendor is AMD.

This will:

- Make sure we don't set the feature bit aliases on Intel CPUs;
- Make it easier to convert feature bits to CPU properties, as now we
  have a single bit on the x86_def_t struct for each CPU feature.

Signed-off-by: Eduardo Habkost <[email protected]>
Reviewed-by: Don Slutz <[email protected]>
Signed-off-by: Blue Swirl <[email protected]>