Bank of America Corp. (NYSE: BAC) reported a lackluster quarter Thursday morning, but its mobile banking business is thriving. The Charlotte, N.C.-based bank added 2.5 million mobile banking customers in the last year. The number of total active users is up to 19.6 million this quarter, up from 18.7 million last quarter and up from 17.1 million in the first quarter of 2015. Bank executives touted mobile banking progress on a call with investors and analysts to discuss first-quarter results Thursday.…