staging: dgap: remove unneeded status variables

dgap_driver_start and dgap_Major_Control_Registered are used
to keep status of initialization of the driver as a whole and its "Major Control".
But the code that checks them is executed once on module init/unload.
That makes no sense in these variables as far as their values are predictable
at any time.

Also "dgap_downld" device was removed, while
device_destroy(MKDEV(DIGI_DGAP_MAJOR, 1)) is still in dgap_cleanup_module().
The patch removes it by the way.

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>