dt-bindings: interrupt-controller: Update Loongson HTVEC description

Loongson HTVEC support 8 parents interrupts in maximum, so update the
maxItems description.
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Link: https://lore.kernel.org/r/1596099090-23516-2-git-send-email-chenhc@lemote.com

Documentation/devicetree/bindings/interrupt-controller/loongson,htvec.yaml

@@ -22,8 +22,8 @@ properties:
 
   interrupts:
     minItems: 1
-    maxItems: 4
-    description: Four parent interrupts that receive chained interrupts.
+    maxItems: 8
+    description: Eight parent interrupts that receive chained interrupts.
 
   interrupt-controller: true