drm/gma500/gma_display: Demote kernel-doc abuses to standard comment blocks

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

 drivers/gpu/drm/gma500/gma_display.c:27: warning: Function parameter or member 'crtc' not described in 'gma_pipe_has_type'
 drivers/gpu/drm/gma500/gma_display.c:27: warning: Function parameter or member 'type' not described in 'gma_pipe_has_type'
 drivers/gpu/drm/gma500/gma_display.c:190: warning: Function parameter or member 'crtc' not described in 'gma_crtc_dpms'
 drivers/gpu/drm/gma500/gma_display.c:190: warning: Function parameter or member 'mode' not described in 'gma_crtc_dpms'
 drivers/gpu/drm/gma500/gma_display.c:573: warning: Function parameter or member 'crtc' not described in 'gma_crtc_save'
 drivers/gpu/drm/gma500/gma_display.c:616: warning: Function parameter or member 'crtc' not described in 'gma_crtc_restore'

Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Eric Anholt <eric@anholt.net>
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/20210115181313.3431493-22-lee.jones@linaro.org