Fix a syntax error in /cpu/cc253x/dev/uart0.c
Fix a syntax error in /cpu/cc253x/dev/uart0.c

bluerover/6lbr,bluerover/6lbr,MohamedSeliem/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,bluerover/6lbr,bluerover/6lbr,arurke/contiki,MohamedSeliem/contiki,arurke/contiki,bluerover/6lbr,bluerover/6lbr,MohamedSeliem/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,arurke/contiki,bluerover/6lbr