[SPARC] display7seg: implement ->unlocked_ioctl and ->compat_ioctl

all ioctls are 32bit compat clean, so the driver can use ->compat_ioctl
and ->unlocked_ioctl easily.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>