MIPS: PCI: Use struct list_head lists

MIPS: PCI: Use struct list_head lists

Rather than open-coding a linked list implementation, make use of the
one in linux/list.h.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14340/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>