drm/i915: Mark i915.inject_load_failure as being hit

When we reach the magic value and do inject a fault into our module load,
mark the module option as being hit. Since we fail from inside pci
probe, the module load isn't actually aborted and the module (and
parameters) are left lingering. igt can then inspect the parameter on its
synchronous completion of modprobe to see if the fault injection was
successful, and will keeping on injecting new faults until the module
succeeds in loading having surpassed the number of fault points.

v2: Reset to 0 after being hit;

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180606144153.4244-1-chris@chris-wilson.co.uk