video/sis/: remove compat code

This patch removes compat code for older kernel versions.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: <thomas@winischhofer.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>