KVM: nSVM: Always inject a #GP if mapping VMCB12 fails on nested VMRUN

KVM: nSVM: Always inject a #GP if mapping VMCB12 fails on nested VMRUN

nested_svm_vmrun() currently only injects a #GP if kvm_vcpu_map() fails
with -EINVAL. But it could also fail with -EFAULT if creating a host
mapping failed. Inject a #GP in all cases, no reason to treat failure
modes differently.

Fixes: 8c5fbf1a7231 ("KVM/nSVM: Use the new mapping API for mapping guest memory")
CC: stable@vger.kernel.org
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-6-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>