doxygen/UART: don't include overridden typedefs
doxygen/UART: don't include overridden typedefs

Add missing #ifndefs to overridden UART typedefs.

Signed-off-by: Yegor Yefremov <379041fa42359f10443de1f461b1b247ec449fae@googlemail.com>

OlegHahm/RIOT,yogo1212/RIOT,x3ro/RIOT,x3ro/RIOT,josephnoir/RIOT,aeneby/RIOT,yogo1212/RIOT,kaspar030/RIOT,smlng/RIOT,kaspar030/RIOT,ant9000/RIOT,x3ro/RIOT,authmillenon/RIOT,basilfx/RIOT,toonst/RIOT,kaspar030/RIOT,toonst/RIOT,basilfx/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,authmillenon/RIOT,smlng/RIOT,mtausig/RIOT,aeneby/RIOT,josephnoir/RIOT,authmillenon/RIOT,toonst/RIOT,kYc0o/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,smlng/RIOT,basilfx/RIOT,ant9000/RIOT,jasonatran/RIOT,OTAkeys/RIOT,miri64/RIOT,miri64/RIOT,jasonatran/RIOT,kYc0o/RIOT,yogo1212/RIOT,kYc0o/RIOT,aeneby/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,toonst/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,miri64/RIOT,RIOT-OS/RIOT,basilfx/RIOT,kaspar030/RIOT,authmillenon/RIOT,mtausig/RIOT,josephnoir/RIOT,RIOT-OS/RIOT,x3ro/RIOT,ant9000/RIOT,kaspar030/RIOT,toonst/RIOT,jasonatran/RIOT,mtausig/RIOT,basilfx/RIOT,yogo1212/RIOT,authmillenon/RIOT,OlegHahm/RIOT,mtausig/RIOT,OTAkeys/RIOT,smlng/RIOT,miri64/RIOT,OTAkeys/RIOT,ant9000/RIOT,ant9000/RIOT,x3ro/RIOT,miri64/RIOT,jasonatran/RIOT,smlng/RIOT,jasonatran/RIOT,yogo1212/RIOT,kYc0o/RIOT,aeneby/RIOT,josephnoir/RIOT,kYc0o/RIOT,mtausig/RIOT,aeneby/RIOT,OTAkeys/RIOT,josephnoir/RIOT