ARM: davinci: Check for NULL return from irq_alloc_generic_chip

Avoid NULL dereference of irq_alloc_generic_chip return in low
memory conditions.
Signed-off-by: NTodd Poynor <toddpoynor@google.com>
Signed-off-by: NSekhar Nori <nsekhar@ti.com>

arch/arm/mach-davinci/irq.c

@@ -52,6 +52,12 @@ davinci_alloc_gc(void __iomem *base, unsigned int irq_start, unsigned int num)
 	struct irq_chip_type *ct;
 
 	gc = irq_alloc_generic_chip("AINTC", 1, irq_start, base, handle_edge_irq);
+	if (!gc) {
+		pr_err("%s: irq_alloc_generic_chip for IRQ %u failed\n",
+		       __func__, irq_start);
+		return;
+	}
+
 	ct = gc->chip_types;
 	ct->chip.irq_ack = irq_gc_ack;
 	ct->chip.irq_mask = irq_gc_mask_clr_bit;