staging: dgnc: remove useless error value assignment

The "result" variable in dgnc_get_mstat() was initialized with
"-EIO". But if the "ch" is not null, "result" will be set to zero
and if the "ch" is null, dgnc_get_mstat() will return "-ENXIO" as
an error. So "-EIO" error value was useless in dgnc_get_mstat().

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>