Revert "USB: serial: sierra: put reset_resume callback back."

This reverts commit 6971113e.

As Alan pointed out, this really isn't needed as it doesn't handle this
properly.  Ideally this should be handled by the usb-serial core one
day.  So revert it.

Reported-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Johan Hovold <jhovold@gmail.com>
Cc: Anton Samokhvalov <pg83@yandex.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>