KVM: Explicitly mark KVM_GUEST_MEMFD as depending on KVM_GENERIC_MMU_NOTIFIER

Add KVM_GENERIC_MMU_NOTIFIER as a dependency for selecting KVM_GUEST_MEMFD,
as guest_memfd relies on kvm_mmu_invalidate_{begin,end}(), which are
defined if and only if the generic mmu_notifier implementation is enabled.

The missing dependency is currently benign as s390 is the only KVM arch
that doesn't utilize the generic mmu_notifier infrastructure, and s390
doesn't currently support guest_memfd.

Fixes: a7800aa ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20251003232606.4070510-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

virt/kvm/Kconfig

@@ -113,6 +113,7 @@ config KVM_GENERIC_MEMORY_ATTRIBUTES
        bool
 
 config KVM_GUEST_MEMFD
+       depends on KVM_GENERIC_MMU_NOTIFIER
        select XARRAY_MULTI
        bool