init: remove adb forced config and switch to mtp.

-adb is not enabled by default and now requires a whitelist, for security
purposes.  Let's enable MTP in that case and leave the debugging option
up to developer settings.

-Note: the forced adb config was there to allow for adb to start
       without delay on system init, for debugging purposes.
Merge remote-tracking branch 'pershoot/cm-10.1' into cm-10.1