Avoid spurious UsbAlsaJackDetector JNI log

Return the result of jniRegisterNativeMethods directly when registering
JNI methods for UsbAlsaJackDetector. The current implementation
incorrectly logs an error upon success.

Change-Id: I45ebc110191da0d7deda0ff7f5ed66d13e62732b
Test: m + validate removed log
BUG: 199520597