Revert "DWARFVerifier: Check "completeness" of .debug_names section"

The new verifier check has found an error in the
debug-names-name-collisions.ll test on the PS4 bot:

error: Name Index @ 0x0: Entry @ 0xdc: mismatched Name of DIE @ 0x23: index - _ZN3foo3fooE; debug_info - foo.

Reverting while I investigate whether this is a bug in the verifier or
the generator.

This reverts commit r331868.

llvm-svn: 331869