staging: dgnc: Remove unnecessary dgnc_Major_Control_Registered variable

The dgnc_Major_Control_Registered variable purpose was to act as a flag
to indicate if the character device has been successfully registered
into the kernel. This flag was later checked in the module cleanup
function to know if the character device needs to be deregistered.

However the {device,class}_destroy and unregister_chrdev functions may
be called with 'invalid' data perfectly fine. This means that this
variable is not needed and can safely be removed which is what this
commit does.

Signed-off-by: Konrad Zapalowicz <bergo.torino@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>