newport_con: fix no return statement in newport_show_logo

When CONFIG_LOGO_SGI_CLUT224 is unset, newport_show_logo contains no
return, despite it should return a pointer. Add one returning NULL to
fix a compiler warning:
   drivers/video/console/newport_con.c: In function 'newport_show_logo':
   drivers/video/console/newport_con.c:132:1: warning: no return statement in function returning non-void

Note that the caller expects NULL from the function already.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Link: https://lore.kernel.org/r/20200818085655.12071-2-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>