irq_domain: Centralize definition of irq_dispose_mapping()
Several architectures define their own empty irq_dispose_mapping(). Since
the irq_domain code is centralized now, there is little need to do so. This
patch removes them and creates a new empty copy when !CONFIG_IRQ_DOMAIN is
selected.
The patch also means that IRQ_DOMAIN becomes selectable on all architectures.
Signed-off-by: Grant Likely <grant.likely@secretlab.ca> Cc: Rob Herring <rob.herring@calxeda.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Jonas Bonn <jonas@southpole.se> Cc: sparclinux@vger.kernel.org Cc: linux@lists.openrisc.net