Unbreak emulators/visualboyadvance-m

fex/fex/File_Extractor.h:181:58: error: cannot initialize return object of type 'blargg_err_t' (aka 'const char *') with an lvalue of type 'const int'
inline blargg_err_t File_Extractor::rewind_v() { return blargg_ok; }

PR: 223538
Submitted by: w.schwarzenfeld@utanet.at (based on)