powerpc: Merge i8259.c into arch/powerpc/sysdev

This changes the parameters for i8259_init so that it takes two
parameters: a physical address for generating an interrupt
acknowledge cycle, and an interrupt number offset.  i8259_init
now sets the irq_desc[] for its interrupts; all the callers
were doing this, and that code is gone now.  This also defines
a CONFIG_PPC_I8259 symbol to select i8259.o for inclusion, and
makes the platforms that need it select that symbol.

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/ppc/platforms/radstone_ppc7d.c b/arch/ppc/platforms/radstone_ppc7d.c
index 5058568..6f97911 100644
--- a/arch/ppc/platforms/radstone_ppc7d.c
+++ b/arch/ppc/platforms/radstone_ppc7d.c
@@ -514,13 +514,9 @@
 	int irq;
 
 	pr_debug("%s\n", __FUNCTION__);
-	i8259_init(0);
+	i8259_init(0, 0);
 	mv64360_init_irq();
 
-	/* IRQ 0..15 are handled by the cascaded 8259's of the Ali1535 */
-	for (irq = 0; irq < 16; irq++) {
-		irq_desc[irq].handler = &i8259_pic;
-	}
 	/* IRQs 5,6,9,10,11,14,15 are level sensitive */
 	irq_desc[5].status |= IRQ_LEVEL;
 	irq_desc[6].status |= IRQ_LEVEL;