drm/i915/display/intel_wm: Fix a little doc-rot in intel_update_watermarks()

drm/i915/display/intel_wm: Fix a little doc-rot in intel_update_watermarks()

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/i915/display/intel_wm.c:46: warning: Function parameter or member 'i915' not described in 'intel_update_watermarks'
 drivers/gpu/drm/i915/display/intel_wm.c:46: warning: Excess function parameter 'dev_priv' description in 'intel_update_watermarks'

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230331092607.700644-20-lee@kernel.org