antfs: require kernel version 5.10 to build

ANTFS does not compile with OpenWrt's current testing kernel 5.15,
as it needs to be modified for the Linux 5.12 idmapped mounts changes
2f221d6f7b88 ("attr: handle idmapped mounts")
https://lore.kernel.org/all/20210121131959.646623-1-christian.brauner@ubuntu.com/



Signed-off-by: John Thomson <git@johnthomson.fastmail.com.au>