Cleanup some trivial TODOs.

1) There's no reason or way to support boot_clock for waiting for
   property changes, since the underlying futex_wait uses
   CLOCK_MONOTONIC.  We probably wouldn't want boot_clock even if it
   did, since it doesn't make sense to consider the time a device was
   suspending in the timeout for waiting for a property to change.
2) The init tokenizer has been essentially unchanged for a decade,
   there's no motivation to 'fix' it to not require a trailing
   newline.
3) The ueventd TODO regarding moving vendor specific ueventd.rc
   entries out of rootdir has been fixed.

Test: n/a
Change-Id: I3b68e3d2f25cbd539f9f8ff526669b8af04d833d