x86/apic: Provide and use helper for send_IPI_allbutself()

To support IPI shorthands wrap invocations of apic->send_IPI_allbutself()
in a helper function, so the static key controlling the shorthand mode is
only in one place.

Fixup all callers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105220.492691679@linutronix.de

arch/x86/kernel/apic/ipi.c

@@ -50,6 +50,18 @@ void apic_smt_update(void)
 		static_branch_enable(&apic_use_ipi_shorthand);
 	}
 }
+
+void apic_send_IPI_allbutself(unsigned int vector)
+{
+	if (num_online_cpus() < 2)
+		return;
+
+	if (static_branch_likely(&apic_use_ipi_shorthand))
+		apic->send_IPI_allbutself(vector);
+	else
+		apic->send_IPI_mask_allbutself(cpu_online_mask, vector);
+}
+
 #endif /* CONFIG_SMP */
 
 static inline int __prepare_ICR2(unsigned int mask)