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

 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:48: warning: cannot understand function prototype: 'struct vmw_overlay '
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:98: warning: Function parameter or member 'dev_priv' not described in 'vmw_overlay_send_put'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:98: warning: Function parameter or member 'buf' not described in 'vmw_overlay_send_put'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:98: warning: Function parameter or member 'arg' not described in 'vmw_overlay_send_put'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:98: warning: Function parameter or member 'interruptible' not described in 'vmw_overlay_send_put'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:186: warning: Function parameter or member 'dev_priv' not described in 'vmw_overlay_send_stop'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:186: warning: Function parameter or member 'stream_id' not described in 'vmw_overlay_send_stop'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:186: warning: Function parameter or member 'interruptible' not described in 'vmw_overlay_send_stop'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:228: warning: Function parameter or member 'dev_priv' not described in 'vmw_overlay_move_buffer'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:228: warning: Function parameter or member 'buf' not described in 'vmw_overlay_move_buffer'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:228: warning: Function parameter or member 'pin' not described in 'vmw_overlay_move_buffer'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:228: warning: Function parameter or member 'inter' not described in 'vmw_overlay_move_buffer'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:253: warning: Function parameter or member 'dev_priv' not described in 'vmw_overlay_stop'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:253: warning: Function parameter or member 'stream_id' not described in 'vmw_overlay_stop'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:253: warning: Function parameter or member 'pause' not described in 'vmw_overlay_stop'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:253: warning: Function parameter or member 'interruptible' not described in 'vmw_overlay_stop'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:301: warning: Function parameter or member 'dev_priv' not described in 'vmw_overlay_update_stream'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:301: warning: Function parameter or member 'buf' not described in 'vmw_overlay_update_stream'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:301: warning: Function parameter or member 'arg' not described in 'vmw_overlay_update_stream'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:301: warning: Function parameter or member 'interruptible' not described in 'vmw_overlay_update_stream'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:364: warning: Function parameter or member 'dev_priv' not described in 'vmw_overlay_resume_all'
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:398: warning: Function parameter or member 'dev_priv' not described in 'vmw_overlay_pause_all'

Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115181313.3431493-24-lee.jones@linaro.org