MFC r261351, r261352, r261355, r261396, r261397, r261398, r261403, r261404,
r261405

Open Firmware interrupt specifiers can consist of arbitrary-length byte
strings and include arbitrary information (IRQ line/domain/sense). When the
ofw_bus_map_intr() API was introduced, it assumed that, as on most systems,
these were either 1 cell, containing an interrupt line, or 2, containing
a line number plus a sense code. It turns out a non-negligible number of
ARM systems use 3 (or even 4!) cells for interrupts, so make this more
general.

Provide a simpler and more standards-compliant simplebus implementation to
get the Routerboard 800 up and running with the vendor device tree. This
does not implement some BERI-specific features (which hopefully won't be
necessary soon), so move the old code to mips/beri, with a higher attach
priority when built, until MIPS interrupt domain support is rearranged.

Allow nesting of simplebuses.

Add a set of helpers (ofw_bus_get_status() and ofw_bus_status_okay()) to
process "status" properties of OF nodes.

Fix one remnant endian flaw in nexus.

MFC r261351, r261352, r261355, r261396, r261397, r261398, r261403, r261404,
r261405

Open Firmware interrupt specifiers can consist of arbitrary-length byte
strings and include arbitrary information (IRQ line/domain/sense). When the
ofw_bus_map_intr() API was introduced, it assumed that, as on most systems,
these were either 1 cell, containing an interrupt line, or 2, containing
a line number plus a sense code. It turns out a non-negligible number of
ARM systems use 3 (or even 4!) cells for interrupts, so make this more
general.

Provide a simpler and more standards-compliant simplebus implementation to
get the Routerboard 800 up and running with the vendor device tree. This
does not implement some BERI-specific features (which hopefully won't be
necessary soon), so move the old code to mips/beri, with a higher attach
priority when built, until MIPS interrupt domain support is rearranged.

Allow nesting of simplebuses.

Add a set of helpers (ofw_bus_get_status() and ofw_bus_status_okay()) to
process "status" properties of OF nodes.

Fix one remnant endian flaw in nexus.