staging: dgnc: some off by one bugs

"dgnc_NumBoards" is the number of filled out elements in the
dgnc_Board[] array.  "->nasync" and "->maxports" are the same value.
They are the number of channels in the ->channels[] array so these tests
should be ">=" instead of ">" so we avoid reading past the end of the
arrays.

I cleaned up the conditions in dgnc_mgmt_ioctl() a bit.  There was a
work around for the off by one bug in the case where there were no
boards which is no longer needed.  "channel" is unsigned so it can't be
negative.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>