trace/simple: Fix compiler warning for 32 bit hosts

gcc complains when a 32 bit pointer is casted to a 64 bit integer.

Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

scripts/tracetool/backend/simple.py

@@ -79,7 +79,7 @@ def c(events):
                        )
                 # pointer var (not string)
                 elif type_.endswith('*'):
-                    out('    trace_record_write_u64(&rec, (uint64_t)(uint64_t *)%(name)s);',
+                    out('    trace_record_write_u64(&rec, (uintptr_t)(uint64_t *)%(name)s);',
                         name = name,
                        )
                 # primitive data type