init: Blank framebuffer to clear Sony boot splash

Change-Id: If55a9c1e66c17f8005b3c1f49961fc57706f6613
init: fixes for encrypted devices

Postpone some /data setup until post-fs-data, so it applies to
decrypted mounts.

Also enable the sensors service, still in class main, so that it's
running for both the decryption screen (if enabled) and final boot
state.  Fixes CYAN-4682 (reported for rhine).

Change-Id: Idc8c84b0fb5cbe2db1f202cd3bc6d84b589eb70e