tools: bpftool: add raw_tracepoint_writable prog type to header

From commit 9df1c28b ("bpf: add writable context for raw tracepoints"),
a new type of BPF_PROG, RAW_TRACEPOINT_WRITABLE has been added.

Since this BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE is not listed at
bpftool's header, it causes a segfault when executing 'bpftool feature'.

This commit adds BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE entry to
prog_type_name enum, and will eventually fixes the segfault issue.

Fixes: 9df1c28b

 ("bpf: add writable context for raw tracepoints")
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>