drm/i915: Rename "inject_load_failure" module parameter

Commit f2db53f1

 ("drm/i915: Replace "_load" with "_probe"
consequently") deliberately left the name of the module parameter
unchanged as that would require a corresponding change on IGT size.
Now as the IGT side change has been submitted, complete the switch to
the "probe" nomenclature.

Suggested-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: Michał Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Piotr Piórkowski <piotr.piorkowski@intel.com>
Cc: Tomasz Lis <tomasz.lis@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191029102036.6326-3-janusz.krzysztofik@linux.intel.com