linux-imx

doc: md: Fix a file name to md-fault.c in fault-injection.txt

drivers/md/faulty.c has been renamed to md-faulty.c after
following commit merged int to the main line.

  935fe0983e09f4f7331ebf5ea4ae2124f6e9f9e8 .

But the file name in fault-injection.txt has not been changed.
Now the actual file name and document are in sync.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>