kvm: remove .done from struct kvm_async_pf

kvm: remove .done from struct kvm_async_pf

'.done' is used to mark the completion of 'async_pf_execute()', but
'cancel_work_sync()' returns true when the work was canceled, so we
use it instead.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 98fda169290b3b28c0f2db2b8f02290c13da50ef)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>