Remove more semicolons at the end of namespaces

These warnings are triggered by -Wextra-semi (and not -Weverything, as
incorrectly mentioned in I49b6e6af483e011632e6a34c0663c93e5c385aa6).
This warning is added to Hidl-generated libs.

To appease clang-format, this patch also fixes some extra newlines.

Test: Build
Change-Id: I63cf5d8ecba46ad87876ff21848bfff04b12ec6e