emulators/rpcs3: unbreak build on aarch64 after ee309cdf6c6f

Utilities/Thread.cpp:1799:48: error: comparison of integers of different signs: 'uptr' (aka 'unsigned long') and '__register_t' (aka 'long') [-Werror,-Wsign-compare]

const bool is_executing = uptr(info->si_addr) == RIP(context);
                          ~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~

Reported by: pkg-fallout