util-linux: include/mount-api-utils: avoid using sys/mount.h

util-linux: include/mount-api-utils: avoid using sys/mount.h

Avoid compile error:
| In file included from /usr/include/linux/fs.h:19,
|                  from /usr/include/linux/btrfs.h:29,
|                  from ../sources/util-linux-2.41.1/libmount/src/btrfs.c:18:
| /usr/include/x86_64-linux-gnu/sys/mount.h:35:3: \
                   error: expected identifier before numeric constant
|    35 |   MS_RDONLY = 1,                /* Mount read-only.  */
|       |   ^~~~~~~~~

This is seen on PopOS 22.04, an Ubuntu/Debian-based distro.

Signed-off-by: Randy MacLeod <Randy.MacLeod@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>