[PATCH] USB: check for device in zd1201_resume

My patch adding PM support for zd1201 didn't check for the device on
resume, which can oops if the device has been removed.

This patch fixes it.

Signed-off-by: Colin Leroy <colin@colino.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>