MIPS: TXx9: Add __init_refok annotation to quirk_slc90e66_bridge

This pci fixup routine calls __init functions.
In general pci fixup routine must not call __init functions,
but this pci/isa bridge device is not hotpluggable anyway.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7215/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>