configs/orangepipc: add host-dosfstools

genimage from the post-image script needs mkdosfs to create fat partition:

>>>   Executing post-image script board/orangepi/orangepipc/post-image.sh
sh: 1: mkdosfs: not found
vfat(boot.vfat): failed to generate boot.vfat

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>