AT&T ( NYSE: T ) really needs the iPhone, but the iPhone doesn’t need AT&T. That little fact alone is probably enough to give Apple ( NSDQ: AAPL )’s Tim Cook reason to look for another iPhone carrier in the US. Add to that this recent survey from PriceGrabber.com and things are looking bad for AT&T. According to the poll, about 10% of respondents already owned an iPhone, which is great. But, a resounding 34% of respondents indicated that they will avoid buying an iPhone because it wo