staging: dgnc: remove redundant memset call

The brd is allocated by kzalloc() in dgnc_found_board()
so do not need to set 0 to member variable.

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