microblaze/PCI: Remove pci_phys_mem_access_prot() dead code

pci_phys_mem_access_prot() is defined but never used.  Remove it.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20220121205150.1151607-1-helgaas@kernel.org


Signed-off-by: Michal Simek <michal.simek@xilinx.com>