staging: dgnc: DGNC_VERIFY_BOARD macro in do while block

Enclose the body of the multi-statement DGNC_VERIFY_BOARD macro inside a
do - while block as per Documentation/CodingStyle.  Fixes 1 error found
by checkpatch.pl.

Cc: Lidza Louina <lidza.louina@gmail.com>
Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>