Fix occurrences of Wextra-semi-stmt

Bug: http://b/123023349

Upcoming clang update adds a new diagnostic about empty statements from
extraneous semicolons.  Remove the semicolon at the end of DNG_ASSERT
since most uses of the macro treat it as a function call and add a
semicolon after the macro statement.  Fix the one use of DNG_ASSERT that
wasn't using a macro.

Test: Build with new clang.
Change-Id: I7c53fe4d19441446e2c5b7871b4bf07dfffd154c
2 files changed