spmi: pmic-arb: revert "disassociate old virq if hwirq mapping already exists"

Now that spmi-gpio is a proper hierarchical IRQ chip, and all in-tree
users of device tree have been updated, we can now drop the hack that
was introduced to disassociate the old Linux virq if a hwirq mapping
already exists. That patch was introduced to not break git bisect for
any existing boards.

Driver was tested using gpio-keys and iadc/vadc on the LG Nexus 5
(hammerhead) phone.
Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/spmi/spmi-pmic-arb.c

@@ -745,15 +745,10 @@ static int qpnpint_irq_domain_map(struct spmi_pmic_arb *pmic_arb,
 				  irq_hw_number_t hwirq, unsigned int type)
 {
 	irq_flow_handler_t handler;
-	unsigned int old_virq;
 
 	dev_dbg(&pmic_arb->spmic->dev, "virq = %u, hwirq = %lu, type = %u\n",
 		virq, hwirq, type);
 
-	old_virq = irq_find_mapping(domain, hwirq);
-	if (old_virq)
-		irq_domain_disassociate(domain, old_virq);
-
 	if (type & IRQ_TYPE_EDGE_BOTH)
 		handler = handle_edge_irq;
 	else if (type & (IRQ_TYPE_LEVEL_LOW | IRQ_TYPE_LEVEL_HIGH))