drm/i915/display: Drop kerneldoc for 'intel_atomic_commit'

intel_atomic_commit() is not for use internally, but only as an entry
point from the core drm atomic helper (drm_atomic_commit).

Squelches the warning for:
drivers/gpu/drm/i915/display/intel_display.c:14148: warning: Function parameter or member '_state' not described in 'intel_atomic_commit'
drivers/gpu/drm/i915/display/intel_display.c:14148: warning: Excess function parameter 'state' description in 'intel_atomic_commit'

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190712134234.29893-1-chris@chris-wilson.co.uk