MFC r259101:

drm/radeon: agp_info->ai_aperture_size is in bytes, not Mbytes

This fixes radeon_agp_init() and gtt_size is now correct. However, this
is not enough to make Radeon AGP cards work: ttm_agp_backend.c isn't
implemented yet.

Submitted by:	tijl@
MFC     r257991, r257992, 257993, 258504

r257991:
  Consolidate Apple firmware hacks and improve them by switching on the
  presence of mac-io devices in the tree, which uniquely identifies Apple
  hardware.

r257992:
  Allow OF_decode_addr() to also be able to map resources on big-endian
  devices. To this end, make PCI device detection rely on the device_type
  field rather than name, as per the standard.

r257993:

  Make tsec work with the device tree present on the RB800. The previous code
  assumed that the MDIO bus was a direct child of the Ethernet interface. It
  may not be and indeed on many device trees is not. While here, add proper
  locking for MII transactions, which may be on a bus shared by several MACs.

r258504:

  Save and restore the trap vectors when doing OF calls on pSeries machines.

  It turned out that on pSeries machines the call into OF modified the trap
  vectors and this made further behaviour unpredictable.

  With this commit I'm now able to boot multi user on a network booted
  environment on my IntelliStation 285. This is a POWER5+ machine.