Removing syscall_fmt::err_msg and instead always formatting negative
returns as errno values.

With this we can remove a lot of entries that have no special handling
besides the ones we can do by looking at the tracefs format files, i.e.
the types for the fields (e.g. pid_t), well known names (e.g. fd).

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-rg9u7a3qqdnzo37d212vnz2o@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>