NEW YORK (Reuters) - U.S. regulators are scrutinizing the books of some top Wall Street brokers and investment banks for subprime-mortgage losses, according to a report in the online version of the Wall Street Journal. Under review by the U.S. Securities and Exchange Commission is whether the firms are calculating the value of subprime-mortgage assets in a consistent way, as well as customer assets, such as those held for hedge funds, according to the report, which cited people familiar with the inquiry. The regulatory checks, which are expected to include Wall Street's five biggest investment banks including Goldman Sachs Group...