sbus: char: Move D7S_MINOR to include/linux/miscdevice.h

This patch move the define for D7S_MINOR to include/linux/miscdevice.h.
It's better that all minor number are in the same place.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>