tracepoint: Do not rename __data_loc fields to data_loc_<name>
tracepoint: Do not rename __data_loc fields to data_loc_<name>

It's unclear why the renaming exists. It's not like the renamed field
name made __data_loc fields work properly.

This makes things more predictable.

Note that this will break the workaround described in #999 .

iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace