Doxygen: Amend minor issues (#2593)

Corrects a few issues with regards to Doxygen documentation, for example:

- Incorrect parameter referencing.
- Missing @param tags.
- Typos in @param tags.

and a few minor other issues.

src/citra_qt/hotkeys.h

@@ -29,6 +29,8 @@ void RegisterHotkey(const QString& group, const QString& action,
 /**
  * Returns a QShortcut object whose activated() signal can be connected to other QObjects' slots.
  *
+ * @param group  General group this hotkey belongs to (e.g. "Main Window", "Debugger").
+ * @param action Name of the action (e.g. "Start Emulation", "Load Image").
  * @param widget Parent widget of the returned QShortcut.
  * @warning If multiple QWidgets' call this function for the same action, the returned QShortcut
  * will be the same. Thus, you shouldn't rely on the caller really being the QShortcut's parent.