mm: drop support of non-linear mapping from fault codepath

mm: drop support of non-linear mapping from fault codepath

commit 9b4bdd2ffab9557ac43af7dff02e7dab1c8c58bd upstream.

We don't create non-linear mappings anymore.  Let's drop code which
handles them on page fault.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.16:
 - Deleted code is slightly different
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>