drm/qxl: Change drm_fb_helper_sys_*() calls to sys_*()

Now that drm_fb_helper gets deferred io support, the
drm_fb_helper_sys_{fillrect,copyarea,imageblit} functions will schedule
a worker that will call the (struct drm_framebuffer *)->funcs->dirty()
function. This will break this driver so use the
sys_{fillrect,copyarea,imageblit} functions directly.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1461856717-6476-3-git-send-email-noralf@tronnes.org