KVM: x86/mmu: Set Dirty bit for new SPTEs, even if _hardware_ A/D bits are disabled

When making a SPTE, set the Dirty bit in the SPTE as appropriate, even if
hardware A/D bits are disabled.  Only EPT allows A/D bits to be disabled,
and for EPT, the bits are software-available (ignored by hardware) when
A/D bits are disabled, i.e. it is perfectly legal for KVM to use the Dirty
to track dirty pages in software.

Link: https://lore.kernel.org/r/20241011021051.1557902-17-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>