KVM: x86: Remove obsolete disabling of page faults in kvm_arch_vcpu_put()

Remove the disabling of page faults across kvm_steal_time_set_preempted()
as KVM now accesses the steal time struct (shared with the guest) via a
cached mapping (see commit b0431382

, "x86/KVM: Make sure
KVM_VCPU_FLUSH_TLB flag is not missed".)  The cache lookup is flagged as
atomic, thus it would be a bug if KVM tried to resolve a new pfn, i.e.
we want the splat that would be reached via might_fault().

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210123000334.3123628-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>