cpu/cc26x2_cc13x2: fix boolean logic for osc change
cpu/cc26x2_cc13x2: fix boolean logic for osc change

Small typo on the loop that checks that the oscillator is ready to be
changed.

Signed-off-by: Jean Pierre Dudey <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@jeandudey.tech>

RIOT-OS/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,miri64/RIOT,jasonatran/RIOT,miri64/RIOT,miri64/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,ant9000/RIOT,authmillenon/RIOT,kaspar030/RIOT,kYc0o/RIOT,kaspar030/RIOT,OlegHahm/RIOT,ant9000/RIOT,authmillenon/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,kYc0o/RIOT,ant9000/RIOT,jasonatran/RIOT,authmillenon/RIOT,authmillenon/RIOT,jasonatran/RIOT,OTAkeys/RIOT,ant9000/RIOT,jasonatran/RIOT,miri64/RIOT,OTAkeys/RIOT,authmillenon/RIOT,ant9000/RIOT,kaspar030/RIOT,kYc0o/RIOT,authmillenon/RIOT,kaspar030/RIOT,kYc0o/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,miri64/RIOT,OTAkeys/RIOT