staging: dgap: remove unneeded dgap_driver_states

The only driver states we need now is READY or !READY.
No need for a sysfs method of seeing those 2 states so
the sysfs entries for dgap_driver_state is also removed.

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