staging: dgap: Fix how we insure config data is a string

This patch changes the way we insure the config data
is a string. Clearly this was just wrong. After a
certain number of loads/unloads various OOPs were
generated indicating something other than this driver
had a problem. It was this driver.

Signed-off-by: Mark Hounschell <markh@compro.net>
Tested-by: Mark Hounschell <markh@compro.net>
Reported-by: Mark Hounschell <markh@compro.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>