board: starfive: Fixed errors reported when executing get_maintainer.pl

Fixed errors reported when executing 'scripts/get_maintainer.pl -f
configs/starfive_visionfive2_defconfig'.

Invalid MAINTAINERS address: 'startfive'

Signed-off-by: Yanhong Wang <yanhong.wang@starfivetech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>