irqchip/mbigen: Handle multiple device nodes in a mbigen module

Each mbigen device is represented as a independent platform device. If the
devices belong to the same mbigen hardware module, then the register space for
these devices is the same. That leads to a resource conflict.

The solution for this is to represent the mbigen module as a platform device
and make the mbigen devices subdevices of that. The register space is
associated to the mbigen module and therefor the resource conflict is avoided.

[ tglx: Massaged changelog, cleaned up the code and removed the silly printk ]

Signed-off-by: Ma Jun <majun258@huawei.com>
Cc: mark.rutland@arm.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/1458203641-17172-3-git-send-email-majun258@huawei.com


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