fault-injection: fix example scripts in documentation

Fix and cleanup example scripts in fault injection documentation.

1. Eliminate broken oops() shell function.

2. Fold failcmd.sh and failmodule.sh into example scripts. It makes
   the example scripts work independent of current working directory.

3. Set "space" parameter to 0 to start injecting errors immediately.

4. Use /sys/module/<modulename>/sections/.data as upper bound of
   .text section. Because some module doesn't have .exit.text section.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>