[PATCH 2/3] wistron_btns: Generic keymap

This patch adds a generic map. That is, a keymap that should output the correct keycodes for most laptops. This is simply based on the observation of all those keymaps already gathered, as most of the wistron codes are always mapped to the same keycode.

Hopefully, this way users which have a non-supported laptop will have a quick and dirty way to use the multimedia keys.

Eric