Revert "fb_defio: fix for non-dirty ptes"

This reverts commit 49bbd815 ("fb_defio:
fix for non-dirty ptes").

Although the fix provided is correct, it's been suggested to avoid the
underlying race in the same way as it is currently done in filesystems
like NFS, for maintainability.

A following patch "fb_defio: redo fix for non-dirty ptes" will provide
such an alternate fix.

Signed-off-by: Albert Herranz <albert_herranz@yahoo.es>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>