PCI: microchip: Make some symbols static

PCI: microchip: Make some symbols static

The sparse tool complains as follows:

drivers/pci/controller/pcie-microchip-host.c:304:18: warning:
 symbol 'pcie_event_to_event' was not declared. Should it be static?
drivers/pci/controller/pcie-microchip-host.c:310:18: warning:
 symbol 'sec_error_to_event' was not declared. Should it be static?
drivers/pci/controller/pcie-microchip-host.c:317:18: warning:
 symbol 'ded_error_to_event' was not declared. Should it be static?
drivers/pci/controller/pcie-microchip-host.c:324:18: warning:
 symbol 'local_status_to_event' was not declared. Should it be static?

Those symbols are not used outside of pcie-microchip-host.c, so this
commit marks them static.

Link: https://lore.kernel.org/r/20210308094842.3588847-1-weiyongjun1@huawei.com
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Krzysztof Wilczyński <kw@linux.com>