i386: kill off hv_cpuid_check_and_set()

i386: kill off hv_cpuid_check_and_set()

hv_cpuid_check_and_set() does too much:
- Checks if the feature is supported by KVM;
- Checks if all dependencies are enabled;
- Sets the feature bit in cpu->hyperv_features for 'passthrough' mode.

To reduce the complexity, move all the logic except for dependencies
check out of it. Also, in 'passthrough' mode we don't really need to
check dependencies because KVM is supposed to provide a consistent
set anyway.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210608120817.1325125-7-vkuznets@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>