Just like in qemu_opts_print_help(), print the device name as a caption
instead of on every single line, indent all options, add angle brackets
around types, and align the descriptions after 24 characters.  Also,
separate the descriptions with " - " instead of putting them in
parentheses, because that is what we do everywhere else.  This does look
a bit funny here because basically all bits have the description
"on/off", but funny does not mean it is less readable.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>