MIPS: MSP71xx: remove odd locking in PCI config space access code

Caller (generic PCI code) already do proper locking so no need to add
another one here.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Cc: Linux MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/7601/


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