mm/gup.c: make unnecessarily global vma_permits_fault() static

Make vma_permits_fault() static as it is only used in mm/gup.c

This fixes a sparse warning.

Link: http://lkml.kernel.org/r/20161017122353.31598-1-tklauser@distanz.ch
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/gup.c

@@ -632,7 +632,8 @@ next_page:
 	return i;
 }
 
-bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags)
+static bool vma_permits_fault(struct vm_area_struct *vma,
+			      unsigned int fault_flags)
 {
 	bool write   = !!(fault_flags & FAULT_FLAG_WRITE);
 	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);