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

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/include/mtd/Kbuild b/include/mtd/Kbuild
index e1da2a5..13e7a3c 100644
--- a/include/mtd/Kbuild
+++ b/include/mtd/Kbuild
@@ -1,2 +1,6 @@
-unifdef-y := mtd-abi.h
-header-y := inftl-user.h jffs2-user.h mtd-user.h nftl-user.h
+header-y += inftl-user.h
+header-y += jffs2-user.h
+header-y += mtd-user.h
+header-y += nftl-user.h
+
+unifdef-y += mtd-abi.h