staging: dgap: pass "dgap_numboards" as a paramter to dgap_found_board()

- Pass "dgap_numboards" to dgap_found_board() instead of
using a global variable.

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