f2fs: move ioctl interface definitions to separated file

Like other filesystem does, we introduce a new file f2fs.h in path of
include/uapi/linux/, and move f2fs-specified ioctl interface definitions
to that file, after then, in order to use those definitions, userspace
developer only need to include the new header file rather than
copy & paste definitions from fs/f2fs/f2fs.h.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index fe39e591..89c451f 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -31,6 +31,7 @@
 #include "gc.h"
 #include "trace.h"
 #include <trace/events/f2fs.h>
+#include <uapi/linux/f2fs.h>
 
 static vm_fault_t f2fs_filemap_fault(struct vm_fault *vmf)
 {