KVM: x86: Inline kvm_get_apic_mode() in lapic.h

KVM: x86: Inline kvm_get_apic_mode() in lapic.h

Inline kvm_get_apic_mode() in lapic.h to avoid a CALL+RET as well as an
export.  The underlying kvm_apic_mode() helper is public information, i.e.
there is no state/information that needs to be hidden from vendor modules.

No functional change intended.

Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20241009181742.1128779-5-seanjc@google.com
Link: https://lore.kernel.org/r/20241101183555.1794700-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>