KVM: arm64: nv: Report addrsz fault at level 0 with a bad VTTBR.BADDR

As per R_BFHQH,

" When an Address size fault is generated, the reported fault code
  indicates one of the following:

  If the fault was generated due to the TTBR_ELx used in the translation
  having nonzero address bits above the OA size, then a fault at level 0. "

Fix the reported Address size fault level as being 0 if the base address is
wrongly programmed by L1.

Fixes: 61e30b9 ("KVM: arm64: nv: Implement nested Stage-2 page table walk logic")
Signed-off-by: Zenghui Yu (Huawei) <zenghui.yu@linux.dev>
Link: https://patch.msgid.link/20260225173515.20490-3-zenghui.yu@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Zenghui Yu (Huawei)

arch/arm64/kvm/nested.c

@@ -280,7 +280,8 @@ static int walk_nested_s2_pgd(struct kvm_vcpu *vcpu, phys_addr_t ipa,
 	base_addr = wi->baddr & GENMASK_ULL(47, base_lower_bound);
 
 	if (check_output_size(wi, base_addr)) {
-		out->esr = compute_fsc(level, ESR_ELx_FSC_ADDRSZ);
+		/* R_BFHQH */
+		out->esr = compute_fsc(0, ESR_ELx_FSC_ADDRSZ);
 		return 1;
 	}