ARM: dts: armada-385.dtsi: Add definitions for PCIe legacy INTx interrupts

With this change legacy INTA, INTB, INTC and INTD interrupts are reported
separately and not mixed into one Linux virq source anymore.

Signed-off-by: Pali Rohár <pali@kernel.org>
Acked-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Tested-by: Luis Mendes <luis.p.mendes@gmail.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>