staging: dgnc: remove redundant null check in

the "brd" was already checked for NULL before calling dgnc_do_remap().

the dgnc_do_remap() function was called only
from the dgnc_found_board() and the DGNC_BOARD_MAGIC value
was assigned to "brd->magic" in dgcn_found_board(). So it doesn't
need to check about magic value.

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