This patch removes the simplistic implementation of irq_domains and enables
the powerpc infrastructure for all irq_domain users.  The powerpc
infrastructure includes support for complex mappings between Linux and
hardware irq numbers, and can manage allocation of irq_descs.

This patch also converts the few users of irq_domain_add()/irq_domain_del()
to call irq_domain_add_legacy() instead.

v3: Fix bug that set up too many irqs in translation range.
v2: Fix removal of irq_alloc_descs() call in gic driver
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Milton Miller <miltonm@bga.com>
Tested-by: Olof Johansson <olof@lixom.net>