Return a negative errno instead of zero in the write function of
the sysfs entry in case of error.
Also add a check on the return value of dlfb_setup_modes().
Signed-off-by: NOlivier Sobrie <olivier@sobrie.be>
Acked-by: NBernie Thompson <bernie@plugable.com>
Signed-off-by: NFlorian Tobias Schandinat <FlorianSchandinat@gmx.de>