[llvm-nm] Remove one-dash long options except -arch

The documentation and help messages have recommended the double-dash forms for
quite a while. Remove one-dash long options which are not recognized by GNU
style `getopt_long`.

`-arch` is kept as it is in the manpage of classic nm
https://keith.github.io/xcode-man-pages/nm.1.html

Note: the dyldinfo related options don't have a test.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D105948