x86/acpi: Reduce code duplication in mp_override_legacy_irq()

The new function mp_register_ioapic_irq() is a subset of the code in
mp_override_legacy_irq().

Replace the code duplication by invoking mp_register_ioapic_irq() from
mp_override_legacy_irq().

Signed-off-by: Vikas C Sajjan <vikas.cha.sajjan@hpe.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: kkamagui@gmail.com
Cc: linux-acpi@vger.kernel.org
Link: https://lkml.kernel.org/r/1510848825-21965-3-git-send-email-vikas.cha.sajjan@hpe.com

arch/x86/kernel/acpi/boot.c

@@ -342,13 +342,12 @@ acpi_parse_lapic_nmi(struct acpi_subtable_header * header, const unsigned long e
 #ifdef CONFIG_X86_IO_APIC
 #define MP_ISA_BUS		0
 
+static int __init mp_register_ioapic_irq(u8 bus_irq, u8 polarity,
+						u8 trigger, u32 gsi);
+
 static void __init mp_override_legacy_irq(u8 bus_irq, u8 polarity, u8 trigger,
 					  u32 gsi)
 {
-	int ioapic;
-	int pin;
-	struct mpc_intsrc mp_irq;
-
 	/*
 	 * Check bus_irq boundary.
 	 */
@@ -357,14 +356,6 @@ static void __init mp_override_legacy_irq(u8 bus_irq, u8 polarity, u8 trigger,
 		return;
 	}
 
-	/*
-	 * Convert 'gsi' to 'ioapic.pin'.
-	 */
-	ioapic = mp_find_ioapic(gsi);
-	if (ioapic < 0)
-		return;
-	pin = mp_find_ioapic_pin(ioapic, gsi);
-
 	/*
 	 * TBD: This check is for faulty timer entries, where the override
 	 *      erroneously sets the trigger to level, resulting in a HUGE
@@ -373,16 +364,8 @@ static void __init mp_override_legacy_irq(u8 bus_irq, u8 polarity, u8 trigger,
 	if ((bus_irq == 0) && (trigger == 3))
 		trigger = 1;
 
-	mp_irq.type = MP_INTSRC;
-	mp_irq.irqtype = mp_INT;
-	mp_irq.irqflag = (trigger << 2) | polarity;
-	mp_irq.srcbus = MP_ISA_BUS;
-	mp_irq.srcbusirq = bus_irq;	/* IRQ */
-	mp_irq.dstapic = mpc_ioapic_id(ioapic); /* APIC ID */
-	mp_irq.dstirq = pin;	/* INTIN# */
-
-	mp_save_irq(&mp_irq);
-
+	if (mp_register_ioapic_irq(bus_irq, polarity, trigger, gsi) < 0)
+		return;
 	/*
 	 * Reset default identity mapping if gsi is also an legacy IRQ,
 	 * otherwise there will be more than one entry with the same GSI