KVM: x86: remove the unused assigned_dev_head from kvm_arch

Legacy device assignment was dropped years ago. This field is not used
anymore.

Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
Link: https://lore.kernel.org/r/20231019043336.8998-1-liangchen.linux@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: LiangChen77

arch/x86/include/asm/kvm_host.h

@@ -1284,7 +1284,6 @@ struct kvm_arch {
 	 */
 	spinlock_t mmu_unsync_pages_lock;
 
-	struct list_head assigned_dev_head;
 	struct iommu_domain *iommu_domain;
 	bool iommu_noncoherent;
 #define __KVM_HAVE_ARCH_NONCOHERENT_DMA

arch/x86/kvm/x86.c

@@ -12425,7 +12425,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 		goto out_uninit_mmu;
 
 	INIT_HLIST_HEAD(&kvm->arch.mask_notifier_list);
-	INIT_LIST_HEAD(&kvm->arch.assigned_dev_head);
 	atomic_set(&kvm->arch.noncoherent_dma_count, 0);
 
 	/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */