MIPS: Loongson: cs5536_pci: Add a missing include

Add a missing include to get rid of the following sparse warnings:
warning: symbol 'cs5536_pci_conf_write4' was not declared. Should it be static?
warning: symbol 'cs5536_pci_conf_read4' was not declared. Should it be static?

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8526/


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