staging: udlfb: fix incorrect fb_defio implementation for multiple framebuffers

Fix fb_defio bug in udlfb for multiple framebuffers

Previously when using fb_defio with multiple DisplayLink attached displays
udlfb incorrectly used a shared datastructure where it needed to have
one per fb_info struct. This was completely broken and caused all kinds of
problems, including rendering to one framebuffer affecting others.

Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>