drm/i915: Fix kerneldoc warnings for i915_gpu_error

drivers/gpu/drm/i915/i915_gpu_error.c:1815: warning: No description found for parameter 'dev_priv'
drivers/gpu/drm/i915/i915_gpu_error.c:1815: warning: No description found for parameter 'engine_mask'
drivers/gpu/drm/i915/i915_gpu_error.c:1815: warning: No description found for parameter 'error_msg'
drivers/gpu/drm/i915/i915_gpu_error.c:1815: warning: Excess function parameter 'dev' description in 'i915_capture_error_state'

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180208111105.32149-1-chris@chris-wilson.co.uk