JP Morgan Chase reigned as the top mortgage servicer at the end of last year in a closely-packed ranking of bank holding companies, while Washington Mutual held a comfortable margin as the top thrift servicer. According to data recently released by federal banking regulators, JP Morgan Chase reported some $348.11 billion in mortgage servicing at the end of 2000, including single-family mortgages in its portfolio and loans serviced for others. Most of that business came