powerpc: 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: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 91bb883..6957cc1 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -782,7 +782,7 @@
 {
 	pmd_t pmd;
 	/*
-	 * For a valid pte, we would have _PAGE_PRESENT or _PAGE_FILE always
+	 * For a valid pte, we would have _PAGE_PRESENT always
 	 * set. We use this to check THP page at pmd level.
 	 * leaf pte for huge page, bottom two bits != 00
 	 */