Recommit r371023 "[lib/ObjectYAML] - Stop calling error(1) when mapping the...

Recommit r371023 "[lib/ObjectYAML] - Stop calling error(1) when mapping the st_other field of a symbol."

Fix: added missing return "return 0;"

Original commit message:
This eliminates one of the error(1) call in this lib.
It is different from the others because happens on a fields mapping stage
and can be easily fixed.

Differential revision: https://reviews.llvm.org/D67150

llvm-svn: 371030