[ARM] Orion: Fix boot crash on Kurobox Pro

The Kurobox Pro crashes when any of the PCI controller registers
are accessed.  This patch adds a function to the Orion PCI handling
code that board support code can call to disable enumerating the
PCI bus entirely, and makes the Kurobox Pro PCI-related init code
call this function.

Signed-off-by: Per Andersson <avtobiff@gmail.com>
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>