drm/i915: Fixup kerneldoc

drivers/gpu/drm/i915/intel_display.c:569: warning: Function parameter or member 'dev_priv' not described in 'intel_PLL_is_valid'
drivers/gpu/drm/i915/intel_display.c:569: warning: Function parameter or member 'limit' not described in 'intel_PLL_is_valid'
drivers/gpu/drm/i915/intel_display.c:569: warning: Function parameter or member 'clock' not described in 'intel_PLL_is_valid'
drivers/gpu/drm/i915/intel_display.c:4769: warning: Function parameter or member 'crtc_state' not described in 'skl_update_scaler_plane'
drivers/gpu/drm/i915/intel_display.c:4769: warning: Excess function parameter 'state' description in 'skl_update_scaler_plane'
drivers/gpu/drm/i915/intel_display.c:4967: warning: Function parameter or member 'new_crtc_state' not described in 'intel_post_enable_primary'
drivers/gpu/drm/i915/intel_display.c:12650: warning: Function parameter or member 'new_state' not described in 'intel_prepare_plane_fb'
drivers/gpu/drm/i915/intel_display.c:12650: warning: Excess function parameter 'fb' description in 'intel_prepare_plane_fb'
drivers/gpu/drm/i915/intel_display.c:12763: warning: Function parameter or member 'old_state' not described in 'intel_cleanup_plane_fb'
drivers/gpu/drm/i915/intel_display.c:12763: warning: Excess function parameter 'fb' description in 'intel_cleanup_plane_fb'

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180214134922.28761-2-chris@chris-wilson.co.uk