fix warning "statement is unreachable" in file ff.cpp in FATFileSystem/ChaN

Dependencies:   FATFileSystem

Dependents:   HTTP_SDcard_file_server HTTP_SDcard_file_server_WIZwiki-W7500 httpServer-WIZwiki-W7500 GT511C3_TimeStamp_WIZwiki-W7500 ... more

Fork of SDFileSystem by mbed official

Revision:
4:f242d7bdef28
Parent:
1:7153ee70df01