drm/i915: make update_wm take a dev_priv.

The crtc was never being used here.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/70438bface47fa683cda8a9e95d0556fca448172.1632869550.git.jani.nikula@intel.com