[HEADERS] One line per header in Kbuild files to reduce conflicts

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/include/video/Kbuild b/include/video/Kbuild
index 76a6073..a14f9c0 100644
--- a/include/video/Kbuild
+++ b/include/video/Kbuild
@@ -1 +1 @@
-unifdef-y := sisfb.h
+unifdef-y += sisfb.h