Fix -Wformat-pedantic warning

/work/llvm-3.8/llvm.src/tools/lldb/source/API/SBProcess.cpp:1003:73:
error: format specifies type 'void *' but the argument has type 'lldb_private::Event *' [-Werror,-Wformat-pedantic]
        log->Printf ("SBProcess::%s (event.sp=%p) => %d", __FUNCTION__, event.get(), ret_val);
                                              ~~                        ^~~~~~~~~~~
1 error generated.

llvm-svn: 257692