drm/gma500/mdfld_dsi_output: Demote a couple of kernel-doc formatting abuses

drm/gma500/mdfld_dsi_output: Demote a couple of kernel-doc formatting abuses

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

 drivers/gpu/drm/gma500/mdfld_dsi_output.c:71: warning: Function parameter or member 'dev' not described in 'mdfld_dsi_gen_fifo_ready'
 drivers/gpu/drm/gma500/mdfld_dsi_output.c:71: warning: Function parameter or member 'gen_fifo_stat_reg' not described in 'mdfld_dsi_gen_fifo_ready'
 drivers/gpu/drm/gma500/mdfld_dsi_output.c:71: warning: Function parameter or member 'fifo_stat' not described in 'mdfld_dsi_gen_fifo_ready'
 drivers/gpu/drm/gma500/mdfld_dsi_output.c:95: warning: Function parameter or member 'dsi_config' not described in 'mdfld_dsi_brightness_init'
 drivers/gpu/drm/gma500/mdfld_dsi_output.c:95: warning: Function parameter or member 'pipe' not described in 'mdfld_dsi_brightness_init'

Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: jim liu <jim.liu@intel.com>
Cc: Jackie Li <yaodong.li@intel.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115181601.3432599-22-lee.jones@linaro.org