[POWERPC] pasemi: Allow 8KB config space for I/O bridge

Device 0 function 0 on the root bus is really a two-function bus agent,
but only the first function is visible. Because of this, we need to
allow config accesses into the second range. Modify the check for valid
offsets accordingly.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>