PCI: aardvark: Make symbol 'advk_pci_bridge_emul_ops' static

Fix the following sparse warning:

drivers/pci/controller/pci-aardvark.c:469:28: warning:
 symbol 'advk_pci_bridge_emul_ops' was not declared. Should it be static?

Fixes: 8a3ebd8d ("PCI: aardvark: Implement emulated root PCI bridge config space")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>