MIPS: PCI: Inline pcibios_assign_all_busses

The MIPS implementation of pcibios_assign_all_busses trivially returns
1. Implement it as a static function in asm/pci.h such that the compiler
can inline it & optimise out never-taken paths.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14343/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>