KVM: x86: Re-enter guest if WRMSR(X2APIC_ICR) fastpath is successful

Re-enter the guest in the fastpath if WRMSR emulation for x2APIC's ICR is
successful, as no additional work is needed, i.e. there is no code unique
for WRMSR exits between the fastpath and the "!= EXIT_FASTPATH_NONE" check
in __vmx_handle_exit().

Link: https://lore.kernel.org/r/20240802195120.325560-2-seanjc@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/x86.c

@@ -2195,7 +2195,7 @@ fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu)
 		data = kvm_read_edx_eax(vcpu);
 		if (!handle_fastpath_set_x2apic_icr_irqoff(vcpu, data)) {
 			kvm_skip_emulated_instruction(vcpu);
-			ret = EXIT_FASTPATH_EXIT_HANDLED;
+			ret = EXIT_FASTPATH_REENTER_GUEST;
 		}
 		break;
 	case MSR_IA32_TSC_DEADLINE: