commit 71d126fd upstream.

Some devices lose data on TRIM whether queued or not.  This patch adds
a horkage to disable TRIM.

tj: Collapsed unnecessary if() nesting.
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
[ luis: backported to 3.16:
  - dropped changes to show_ata_dev_trim
  - adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>