video/mbx: fix building debugfs support

The mbx framebuffer debugfs support apparently hasn't been able
to build for a long time, at least since 2006 when the u.generic_ip
field in the inode was removed. This fixes the obvious bug, and
also makes it possible to build the driver as a module when
debugfs support is enabled, by simply including the C file.
It's ugly, but it won't make the driver any worse than it
already is, and doesn't require a more invasive change that
might break it further.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-fbdev@vger.kernel.org
Cc: Raphael Assenat <raph@8d.com>
Cc: Mike Rapoport <mike@compulab.co.il>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>