x86: numachip: Elide self-IPI ICR polling

The default self-IPI path polls the ICR to delay sending the IPI until
there is no IPI in progress. This is redundant on x86-86 APICs, since
IPIs are queued. See the AMD64 Architecture Programmer's Manual, vol 2,
p525.

Signed-off-by: Daniel J Blueman <daniel@numascale.com>
Cc: Steffen Persvold <sp@numascale.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: http://lkml.kernel.org/r/1415089784-28779-2-git-send-email-daniel@numascale.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/apic/apic_numachip.c

@@ -145,7 +145,7 @@ static void numachip_send_IPI_all(int vector)
 
 static void numachip_send_IPI_self(int vector)
 {
-	__default_send_IPI_shortcut(APIC_DEST_SELF, vector, APIC_DEST_PHYSICAL);
+	apic_write(APIC_SELF_IPI, vector);
 }
 
 static int __init numachip_probe(void)