libbinder_ndk: binder_stability.h markVintf weak

This was causing loading errors for Q targets which include this.
Separately, we want to use __INTRODUCED_IN here, but it causes
false positive hits for that static inline void functions which
are declared here.

Bug: 227835797
Test: N/A
Change-Id: I225418b53c7fd83c291ece15cc8f9df3ed37eaad