libbinder_ndk: fix addService return type

This is actually EX_* values, not status values. Right now, we aren't
getting useful error values returned here (luckily they get printed by
PruneStatusT).

Bug: 166822339
Test: TH
Change-Id: Ic4c141e4ea18c34cfec3c256ebb604e696681420
3 files changed