drm/fb: remove unused includes of drm_fb_cma_helper.h

Quite a lot of drivers include the drm_fb_cma_helper.h header file
without actually making use of it's provided API, hence remove those
includes.

Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220802000405.949236-2-dakr@redhat.com