fbcon: Call fbcon_mode_deleted/new_modelist directly

I'm not entirely clear on what new_modelist actually does, it seems
exclusively for a sysfs interface. Which in the end does amount to a
normal fb_set_par to check the mode, but then takes a different path
in both fbmem.c and fbcon.c.

I have no idea why these 2 paths are different, but then I also don't
really want to find out. So just do the simple conversion to a direct
function call.

v2: static inline for the dummy versions, I forgot.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Rosin <peda@axentia.se>
Cc: Yisheng Xie <ysxie@foxmail.com>
Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: linux-fbdev@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190528090304.9388-23-daniel.vetter@ffwll.ch