WifiScanner.ScanData: Address API council feedback

- Rename to getScannedBands()
- Fix typo bistmask -> bitmask
- Clarification of the javadocs.

Bug: 181981365
Test: atest com.android.server.wifi
Change-Id: I7728bd76d4c2c71c1f0650ec34c545fa93ecb6dd
14 files changed