x86, apic: untangle the send_IPI_*() jungle

Our send_IPI_*() methods and definitions are a twisted mess: the same
symbol is defined to different things depending on .config details,
in a non-transparent way.

 - spread out the quirks into separately named per apic driver methods

 - prefix the standard PC methods with default_

 - get rid of wrapper macro obfuscation

 - clean up various details

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index f8536fe..38dace2 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -651,7 +651,7 @@
 
 static void smp_send_nmi_allbutself(void)
 {
-	send_IPI_allbutself(NMI_VECTOR);
+	apic->send_IPI_allbutself(NMI_VECTOR);
 }
 
 static struct notifier_block crash_nmi_nb = {