x86: Unify 3 similar ways of saving mp_irqs info

There are 3 places defining similar functions of saving IRQ vector
info into mp_irqs[] array: mmparse/acpi/mrst.

Replace the redundant code by a common function in io_apic.c as it's
only called when CONFIG_X86_IO_APIC=y

Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <20101207133204.4d913c5a@feng-i7>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index 107f2d8..f327d38 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -184,6 +184,8 @@
 void __init mp_register_ioapic(int id, u32 address, u32 gsi_base);
 extern void __init pre_init_apic_IRQ0(void);
 
+extern void mp_save_irq(struct mpc_intsrc *m);
+
 #else  /* !CONFIG_X86_IO_APIC */
 
 #define io_apic_assign_pci_irqs 0