Commit 2f48b8f462a03cb92db9e9a7ae1957eb27473965 "nouveau: add platform bus
support" added in -1.0.2 prevents X from starting on a MacBookAir booted via
EFI.

As debugged on IRC with airlied, the cause is that kernel reports "boot_vga"
being "0" for the GeForce 9400M (C79) when efifb is not being used (not
compiled into kernel whereas nouveau is). [booting with efifb built-in causes
"boot_vga" to be "1"]

When there is no other GPU around and KMS (+ fbcon) is active on that GPU X
should accept it as well (or kernel adjust boot_vga as needed even while efifb
is not compiled in/used).

Kernel used if 3.7-rc5 (with efifb disabled), 3.7-rc6 (with efifb built-in)