Expose extra USART config options and fix word length bug #615

Job	Run time
ci (stable, stm32g431, log-itm)	48s
ci (stable, stm32g431, log-semihost,can)	46s
ci (stable, stm32g431, log-rtt,defmt)	50s
ci (stable, stm32g441, log-rtt,defmt)	53s
ci (stable, stm32g441, log-itm)	46s
ci (stable, stm32g473, log-rtt,defmt)	52s
ci (stable, stm32g441, cordic,usb,log-rtt,defmt)	1m 4s
ci (stable, stm32g473, log-itm)	50s
ci (stable, stm32g474,hrtim, log-semihost,can)	43s
ci (stable, stm32g441, log-semihost,can)	1m 1s
ci (stable, stm32g473, cordic,usb,log-rtt,defmt)	54s
ci (stable, stm32g474,hrtim, log-rtt,defmt)	54s
ci (stable, stm32g474,hrtim, cordic,usb,log-rtt,defmt)	56s
ci (stable, stm32g473, log-semihost,can)	45s
ci (stable, stm32g483, log-itm)	46s
ci (stable, stm32g474,hrtim, log-itm)	54s
ci (stable, stm32g431, cordic,usb,log-rtt,defmt)	44s
ci (stable, stm32g483, cordic,usb,log-rtt,defmt)	50s
ci (stable, stm32g483, log-rtt,defmt)	53s
ci (stable, stm32g484, log-rtt,defmt)	55s
ci (stable, stm32g483, log-semihost,can)	51s
ci (stable, stm32g484, cordic,usb,log-rtt,defmt)	58s
ci (stable, stm32g484, log-semihost,can)	1m 5s
ci (stable, stm32g491, log-itm)	45s
ci (stable, stm32g4a1, log-rtt,defmt)	49s
ci (stable, stm32g484, log-itm)	43s
ci (stable, stm32g491, cordic,usb,log-rtt,defmt)	52s
ci (stable, stm32g491, log-semihost,can)	46s
ci (stable, stm32g4a1, log-itm)	46s
ci (stable, stm32g4a1, cordic,usb,log-rtt,defmt)	53s
ci (stable, stm32g4a1, log-semihost,can)	44s
ci (stable, stm32g491, log-rtt,defmt)	49s
	27m 5s

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