xtensa: don't use linux IRQ #0

commit e5c86679d5e864947a52fb31e45a425dea3e7fa9 upstream.

Linux IRQ #0 is reserved for error reporting and may not be used.
Increase NR_IRQS for one additional slot and increase
irq_domain_add_legacy parameter first_irq value to 1, so that linux
IRQ #0 is not associated with hardware IRQ #0 in legacy IRQ domains.
Introduce macro XTENSA_PIC_LINUX_IRQ for static translation of xtensa
PIC hardware IRQ # to linux IRQ #. Use this macro in XTFPGA platform
data definitions.

This fixes inability to use hardware IRQ #0 in configurations that don't
use device tree and allows for non-identity mapping between linux IRQ #
and hardware IRQ #.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/irqchip/irq-xtensa-mx.c b/drivers/irqchip/irq-xtensa-mx.c
index bb3ac5f..72a391e 100644
--- a/drivers/irqchip/irq-xtensa-mx.c
+++ b/drivers/irqchip/irq-xtensa-mx.c
@@ -142,7 +142,7 @@
 int __init xtensa_mx_init_legacy(struct device_node *interrupt_parent)
 {
 	struct irq_domain *root_domain =
-		irq_domain_add_legacy(NULL, NR_IRQS, 0, 0,
+		irq_domain_add_legacy(NULL, NR_IRQS - 1, 1, 0,
 				&xtensa_mx_irq_domain_ops,
 				&xtensa_mx_irq_chip);
 	irq_set_default_host(root_domain);