of/irq: Don't ignore interrupt-controller when interrupt-map failed

Since 041284181226 ("of/irq: Allow matching of an interrupt-map local
to an interrupt controller"), the irq code favors using an interrupt-map
over a interrupt-controller property if both are available, while the
earlier behaviour was to ignore the interrupt-map altogether.

However, we now end-up with the opposite behaviour, which is to
ignore the interrupt-controller property even if the interrupt-map
fails to match its input. This new behaviour breaks the AmigaOne
X1000 machine, which ships with an extremely "creative" (read:
broken) device tree.

Fix this by allowing the interrupt-controller property to be selected
when interrupt-map fails to match anything.

Fixes: 041284181226 ("of/irq: Allow matching of an interrupt-map local to an interrupt controller")
Reported-by: Christian Zigotzky <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Cc: Bjorn Helgaas <[e-mail]>

drivers/of/irq.c

···
 		 * if it is then we are done, unless there is an
 		 * interrupt-map which takes precedence.
 		 */
+		bool intc = of_property_read_bool(ipar, "interrupt-controller");
+
 		imap = of_get_property(ipar, "interrupt-map", &imaplen);
-		if (imap == NULL &&
-		    of_property_read_bool(ipar, "interrupt-controller")) {
+		if (imap == NULL && intc) {
 			pr_debug(" -> got it !\n");
 			return 0;
 		}
···
 
 			pr_debug(" -> imaplen=%d\n", imaplen);
 		}
-		if (!match)
+		if (!match) {
+			if (intc) {
+				/*
+				 * The PASEMI Nemo is a known offender, so
+				 * let's only warn for anyone else.
+				 */
+				WARN(!IS_ENABLED(CONFIG_PPC_PASEMI),
+				     "%pOF interrupt-map failed, using interrupt-controller\n",
+				     ipar);
+				return 0;
+			}
+
 			goto fail;
+		}
 
 		/*
 		 * Successfully parsed an interrrupt-map translation; copy new