powerpc/xive: Add a check for memory allocation failure

The result of this kzalloc is not checked. Add a check and corresponding
error handling code.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/cc53462734dfeaf15b6bad0e626b483de18656b4.1564647619.git.christophe.jaillet@wanadoo.fr

arch/powerpc/sysdev/xive/spapr.c

@@ -53,6 +53,10 @@ static int xive_irq_bitmap_add(int base, int count)
 	xibm->base = base;
 	xibm->count = count;
 	xibm->bitmap = kzalloc(xibm->count, GFP_KERNEL);
+	if (!xibm->bitmap) {
+		kfree(xibm);
+		return -ENOMEM;
+	}
 	list_add(&xibm->list, &xive_irq_bitmaps);
 
 	pr_info("Using IRQ range [%x-%x]", xibm->base,