irqchip/GICv2m: Get rid of struct msi_controller

irqchip/GICv2m: Get rid of struct msi_controller

GICv2m only uses the msi_controller structure as a way to match
the host bridge with its MSI HW, and thus the msi_domain.

But now that we can directly associate an msi_domain with a device,
there is no use keeping this msi_controller around.

Just remove all traces of msi_controller from the driver. Also
tag the inner (non-PCI) domain with DOMAIN_BUS_NEXUS.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: Yijing Wang <wangyijing@huawei.com>
Cc: Ma Jun <majun258@huawei.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Duc Dang <dhdang@apm.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/1438091186-10244-17-git-send-email-marc.zyngier@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>