powerpc: Remove file parameter from phys_mem_access_prot()

Remove 'file' parameter from struct machdep_calls.phys_mem_access_prot
and its implementation in pci_phys_mem_access_prot(). The file is not
used on PowerPC. By removing it, a later patch can simplify fbdev's
mmap code, which uses phys_mem_access_prot() on PowerPC.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
[mpe: Rebase on unrelated changes to phys_mem_access_prot()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230922080636.26762-5-tzimmermann@suse.de