[SBUSFB]: implement ->compat_ioctl

This patch adds a new function, sbusfb_compat_ioctl() to
drivers/video/sbuslib.c and uses it as compat_ioctl in all sbus fb
drivers

This remove the last per-arch compat ioctl bits in
arch/sparc64/kernel/ioctl32.c so it would be nice if people could test
if this actually copiles and works and if yes apply it :)

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