irqchip/mbigen: Adjust DT bindings to handle multiple devices in a module

A mbigen hardware module can contain more than one device node. These device
nodes contain the same register definition.

mbigen_dev1:intc_dev1 {
	...
	reg = <0x0 0xc0080000 0x0 0x10000>;
	...
};

mbigen_dev2:intc_dev2 {
	...
	reg = <0x0 0xc0080000 0x0 0x10000>;
	...
};

In this case both devices try to request the same resource resulting in a
resource conflict.

To address this problem the devices need to be subnodes of the mbigen hardware
module, which then contains the unique register space.

[ tglx: Massaged changelog ]

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ma Jun <majun258@huawei.com>
Cc: jason@lakedaemon.net
Cc: marc.zyngier@arm.com
Cc: Catalin.Marinas@arm.com
Cc: guohanjun@huawei.com
Cc: Will.Deacon@arm.com
Cc: huxinwei@huawei.com
Cc: lizefan@huawei.com
Cc: dingtianhong@huawei.com
Cc: zhaojunhua@hisilicon.com
Cc: liguozhu@hisilicon.com
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20160203111602.GA1234@leverpostej
Link: http://lkml.kernel.org/r/1458203641-17172-2-git-send-email-majun258@huawei.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>