socket/option.c: revert r44647

* ext/socket/option.c (NUM2SOCKOPT, sockopt_value): revert because
  these names are confusing.  [ruby-dev:47903]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44656 b2dd03c8-39d4-4d8f-98ff-823fe69b080e