staging: dgap: fix "if" statement that always evaluates to true

cppcheck warning:
(warnning) Logical disjunction always evaluates to true

Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>