KVM: s390: Use kvm_release_page_dirty() to unpin "struct page" memory

Use kvm_release_page_dirty() when unpinning guest pages, as the pfn was
retrieved via pin_guest_page(), i.e. is guaranteed to be backed by struct
page memory.  This will allow dropping kvm_release_pfn_dirty() and
friends.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-81-seanjc@google.com>