Allow reading tainted flag as user

The commit 34f5a398 restricted reading
of the tainted value. The attached patch changes this back to a
write-only check and restores the read behaviour of older versions.

Signed-off-by: Bastian Blank <bastian@waldi.eu.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>