btrfs: fail mount when sb flag is not in BTRFS_SUPER_FLAG_SUPP

btrfs: fail mount when sb flag is not in BTRFS_SUPER_FLAG_SUPP

It appears from the original commit [1] that there isn't any design
specific reason not to fail the mount instead of just warning. This
patch will change it to fail.

[1]
 commit 74658dd15a5579f4c3ca90a36ecaeca2d9ac81d3
    btrfs: Enhance super validation check

Fixes: 74658dd15a5579f ("btrfs: Enhance super validation check")
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>