USB: remove dead code from suspend/resume path

If a driver does not support the suspend/resume callbacks
it will be forcibly disconnected. There is no reason to check
for support of the callbacks after that.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>