kvm: add kvm_{vm,vcpu}_enable_cap

Provide helper functions for enabling capabilities (on a vcpu and on a vm).

Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
s390x: use kvm_vcpu_enable_cap()

Make kvm_s390_enable_css_support() use new interface.

Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
ppc: use kvm_vcpu_enable_cap()

Convert existing users of KVM_ENABLE_CAP to new helper.

Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>