drivers/staging/usbip: bugfix prevent driver unbind regression in linux-next

Fix regression problem in linux-next: post_reset and pre_reset are no longer
included in linux-next while they are in linux-3.0rc5.

Signed-off-by: Arjan Mels <arjan.mels@gmx.net>
Cc: usbip-devel <usbip-devel@lists.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>