target-i386: check/enforce: Eliminate check_feat field

Now that all entries have check_feat=~0 in
kvm_check_features_against_host(), we can eliminate check_feat entirely
and make the code check all bits.

This patch shouldn't introduce any behavior change, as check_feat is set
to ~0 on all entries.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
