KVM: x86: Drop superfluous kvm_lapic_set_base() call when setting APIC state

Now that kvm_lapic_set_base() does nothing if the "new" APIC base MSR is
the same as the current value, drop the kvm_lapic_set_base() call in the
KVM_SET_LAPIC flow that passes in the current value, as it too does
nothing.

Note, the purpose of invoking kvm_lapic_set_base() was purely to set
apic->base_address (see commit 5dbc8f3f ("KVM: use kvm_lapic_set_base()
to change apic_base")).  And there is no evidence that explicitly setting
apic->base_address in KVM_SET_LAPIC ever had any functional impact; even
in the original commit 96ad2cc6 ("KVM: in-kernel LAPIC save and restore
support"), all flows that set apic_base also set apic->base_address to the
same address.  E.g. svm_create_vcpu() did open code a write to apic_base,

	svm->vcpu.apic_base = 0xfee00000 | MSR_IA32_APICBASE_ENABLE;

but it also called kvm_create_lapic() when irqchip_in_kernel() is true.

Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20241009181742.1128779-3-seanjc@google.com
Link: https://lore.kernel.org/r/20241101183555.1794700-3-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>