irqchip/mips-gic: Remove device IRQ domain

In commit c98c1822 ("irqchip/mips-gic: Add device hierarchy domain")
Qais indicates that he felt having a separate device IRQ domain was
cleaner, but along with everyone else I'm aware of touching this driver
I disagree.

Remove the separate device IRQ domain so that we simply have the main
GIC IRQ domain used for devices, and an IPI IRQ domain as a child. The
logic for handling the device interrupts & IPIs is cleanly separated
into the appropriate domain ops, making it much easier to reason about
what the driver is doing than the previous approach where the 2 child
domains had to call up to their parent, which had to handle both types
of interrupt & had all sorts of weird & wonderful duplication or
outright clobbering of setup performed by multiple domains.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Link: http://lkml.kernel.org/r/1492679256-14513-3-git-send-email-matt.redfearn@imgtec.com


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