MIPS: PCI: Reduce stack frame usage

MIPS: PCI: Reduce stack frame usage

This patch removes creating a fake pci device in MIPS early config
access and instead just uses the pci bus to get the same functionality.
The struct pci_dev is too large to allocate on the stack, and was relying
on compiler optimizations to remove its usage.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14253/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>