PCI: hv: Make some functions static

PCI: hv: Make some functions static

sparse report build warning as follows:

drivers/pci/controller/pci-hyperv.c:941:5: warning:
 symbol 'hv_read_config_block' was not declared. Should it be static?
drivers/pci/controller/pci-hyperv.c:1021:5: warning:
 symbol 'hv_write_config_block' was not declared. Should it be static?
drivers/pci/controller/pci-hyperv.c:1090:5: warning:
 symbol 'hv_register_block_invalidate' was not declared. Should it be static?

Those functions are not used outside of this file, so mark them static.

Link: https://lore.kernel.org/r/20200706135234.80758-1-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>