staging: dgap: pass "brd" as a paramter to dgap_after_config_loaded()

Pass "brd" to dgap_after_config_loaded() instead of passing
"dgap_numboards" and looking up brd again.

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