Solaris support for multiple PCI segments (domains)

Solaris support for multiple PCI segments (domains)

1. Removed hardcoded maximum size of 256 PCI devices, which is
too small for large systems.  The number of devices is dynamically
resized as needed.

2. pci_device_solx_devfs_probe() no longer walks the device tree
from the very top ("/") but instead starts at the nexus which
owns the bus.  Performance optimization for systems with multiple
bus nodes (including systems with just one segment/domain).

3. Added support for multiple domains/segments.  Code tested
on kernels with and without multiple segment support so it should
be safe to integrate independent of the kernel version.

Signed-off-by: John Martin <John.M.Martin@Oracle.COM>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>