mips: drop _PAGE_FILE and pte_file()-related helpers

We've replaced remap_file_pages(2) implementation with emulation.  Nobody
creates non-linear mapping anymore.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --cc arch/mips/include/asm/pgtable-32.h
Simple merge

diff --cc arch/mips/include/asm/pgtable-64.h
Simple merge

diff --cc arch/mips/include/asm/pgtable-bits.h
Simple merge

diff --cc arch/mips/include/asm/pgtable.h
Simple merge