Interrelated improvements to early boot mappings:
- Remove explicit requirement that the SOC registers be found except as an
  optimization (although the MPC85XX LAW drivers still require they be found
  externally, which should change).
- Remove magic CCSRBAR_VA value.
- Allow bus_machdep.c's early-boot code to handle non 1:1 mappings and
  systems not in real-mode or global 1:1 maps in early boot.
- Allow pmap_mapdev() on Book-E to reissue previous addresses if the
  area is already mapped. Additionally have it check all mappings, not
  just the CCSR area.

This allows the console on e500 systems to actually work on systems where
the boot loader was not kind enough to set up a 1:1 mapping before starting
the kernel.
Provide includes that are needed in these files, and before were read
in implicitly via if.h -> if_var.h pollution.

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.
Add some extra sanity checking and checks to printf format specifiers.
bump date forgotten in r257165
Be a bit more flexible in how we find the console from the properties on
/chosen, following the list of allowed console properties in ePAPR. Also
do not require that stdin be defined and equal to stdout: stdin is
nonstandard (for ePAPR) and console in an unexpected place is after all
better than no console.
The MII layer shouldn't care about administrative status of an
interface. Make MII drivers forget about 'struct ifnet'.

Later plan is to provide an administrative downcall from ifnet
layer into drivers, to inform them about administrative status
change. If someone thinks that processing MII events for an
administratively down interface is a big problem, then drivers
would turn MII processing off.

The following MII drivers do evil things, like strcmp() on
driver name, so they still need knowledge of ifnet and thus
include if_var.h. They all need to be fixed:

sys/dev/mii/brgphy.c
sys/dev/mii/e1000phy.c
sys/dev/mii/ip1000phy.c
sys/dev/mii/jmphy.c
sys/dev/mii/nsphy.c
sys/dev/mii/rgephy.c
sys/dev/mii/truephy.c

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.